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The analysis of chondritic meteorites
G-eocitiniica et,Cosmochimiea
Acta, 1963, \‘(A. 25, pp. $53 to ;Gi.
Pergamon PressLt,d. Printedin
Xort~hern Ireland
The analysis of chondritic meteorites A. 5. EASTOX and J. I?. LOVERIXG Department of Geophysics, Australian Kational Universit,y Canberra, A.C.T. Australia. (Received
15 September
1962; in revised fornb 11 Janwwy
1963)
Ab&&--A scheme for the analysis of chondritio material (other then volatile rich carbonaceous chondrites) is described which modifies the classical procedures by the introduction of simple ion exchange techniques. The macro constituents of the metallic phase are initially extracted with mercuric-ammonium chloride solution and then separated by elutriation from an anion exchange column. Fe, Ni and Co are then determined by spect.rometric methods without inte~erence from other ions. The al~~urn is separated by ion exchange technique from other members of the R,O, group thereby avoiding the errors of the classical method. K,O and N&,0 are determined by flamephotometry, CaO and iMgO by gravimetric methods or by E.D.T.A titration, and C is centrifuged off, weighed and ignited. Sulphide is determined as sulphate after separation from extraneous ions by ion exchange technique. H,O and CO, are determined by absorption after liberation at 1175°C.
IT HAS long been recognised that the analysis of the “normal” chondritio meteorites {i.e., those chondrites other than the carbonaceous chondrites) poses a number of special problems over and above the usual problems associated with the analysis of silicate rocks and minerals. These special problems arise from the presence of sulphide (also carbide and phosphide) and metallic phases in the chondrites along with silicate and oxide phases. Iron, in various states of oxidation, can exist in each of these phases and it is essential that any analytical scheme should be capable of making accurate determinations of the distribution of the iron content between these various phases co-exist,ing in chondritic meteorites. The analysis of the carbonaceous chondrites poses yet another set of problems because they consist of “amorphous” silicate material as well as crystalline silicates (some hydrated) and oxides (including magnet,ite) with complex mixtures of hydro~arbo~ls, water, ‘~amorphous” carbon, a number of inorganic salts (e.g., MgSO,), and undoubtedly many other materials. The difficulties surrounding the satisfactory analysis of these components are very real and, in fact no completely satisfactory analytical method has yet be devised although the best attempt so far is certainly the work of WIIK (1956). However we have made no attempt in this paper to deal with the analysis of the carbonaceous chondrites. There are over 300 analyses of stony meteorites in the literature but, in view of the difficulties involved, it is not surprising that UREY and CRAIG (1953) concluded that a considerable proportion of these analyses were unsatisfactory and 763
754
A. J.
EASTON
and
J. F. LOVERINC
must be rejected. Many of the analyses date back to the early nineteenth century but not all old analyses are necessarily incorrect. Many of the chondrite analyses carried out by G. T. PRIOR and L. H. BORSTROM over 40 years ago are generally recognised to be of high quality at the present day. The analytical scheme described here owes a great deal to the methods used and developed by WIIK who is recognised to be the most experienced analyst of chondritic meteorites at the present time. In his turn, WIIK acknowledges his indebtedness to W. A. WAHL who was the leader of the previous generation of However we should like to record our very considerable meteorite analysts. indebtedness to WINK in supplying us with details of his methods which have not yet been published. We believe that our analytical scheme for chondritic material does break new ground in that ion exchange resins are used in several steps of the scheme to separate various elements for determination without interferences from other elements. There are other features which should simplify the problems associated with the analysis of chondritic meteorites so that accurate analyses can be carried out in any modern laboratory by a competent analyst without any special previous experience. In this way it is hoped that this analytical scheme will lead to a very badly needed increase in the small number of accurate analyses of chondrites available at the present time. This analytical scheme is extremely flexible and has been used to analyse achondritic meteorites as well as all types of chondritic meteorites. SAMPLING The achondrites and the metal-poor chondrites generally present few problems as far as sampling is concerned. In these meteorites what little metal phase that does occur is generally fine grained and will generally dissolve readily in mercuric chloride-ammonium chloride solutions for subsequent analysis. However the metal-rich chondrites invariably contain large metal grains and even veins of metal which cannot be broken up by normal crushing techniques so that representative sampling becomes very difficult. Furthermore the metal aggregations in these meteorites arc too large to dissolve appreciably in mercuric chlorideammonium chloride and they cannot be separated cleanly from contaminating silicate, sulphide and other phases by any means known to us. In view of the fact that iron becomes brittle at low temperatures, R. RUDOWSKI suggested that metal-rich chondrites might be crushed finely by normal techniques provided the sample was kept near liquid air temperature. An insulated box was constructed to form a reservoir for liquid air storage and an alundum mortar (containing the chondrite sample to be crushed) and pestle was partly immersed in the liquid air through holes cut in the top of the box. After the mortar and sample had been cooled to near liquid air temperature, the metal-rich chondrite was then easily crushed to a fine powder (approximately -200 mesh). After crushing, the mortar was removed from the box and the sample was covered with acetone (to prevent condensation of ice on the sample) and then the sample was gently heated by an infra-red lamp to evaporate the acetone. Using this technique a number of quite metal-rich chondrites have been crushed to powders which pass 200 mesh sieves.
755
The analysis of chondritic meteorites
Once the original chondrite sample has been finely ground, small total sample (i.e., 300-350 mg.) is required for analysis.
only a relatively
AXALYTICAL SCHEME-GENERAL The quantity of chondritic material available for an analysis is generally limited so that it is highly desirable to arrange the analytical procedures in such a way that there is the utmost economy of sample. Even so it would seem that a minimum number of four separate portions are required for a complete analysis: (i) metallic phase, (2) alkalies and minor constituents, (3) sulphide and major Fig. 1 Portion 3.
Portion 1.
11 OXIDATION
METAL EXTRACTION
1OMHCl
Anion column
j Fe
2) E;oLUTI~N IX HF
CO
Cation column
Ni
r
12M HCl
Anion column
O.OlMHCl
so* %O, I
cao MgO
Al,O, Portion 2. SOLTTTION I?uTWFjH,SO, 1 C
CrzO,
I MnO
TiO,
I P,O,
I Total Fe
I Na,O
K,O Portion 5. FUSION Na,C0,‘5)/KN0,‘1’
Portion 4. -Hz0 +H,O CO,
I
Bulk SiO, gravimet,rically / Residual SiO, calorimetrically
constituents and (4) water, CO,. It has also been found desirable to use a fifth portion for the SiO, determination. If SiO, is determined on the same portion used for the major constituent determinations, there is a distinct possibility that incomplete removal of silica (by evaporation and baking, using the normal classical procedure) may lead to precipitation of residual silica at later stages in the analysis. Contamination of other precipitates by this residual silica can cause serious errors in the determination of various elements. In the analytical scheme proposed here a gravimetric determination of the main bulk of silica in a separate portion is followed by calorimetric determination of the residual silica in solution as proposed by JEFFERY and WILSON (1960).
A. J.
756
and J. F.
EASTON
LOVERING
The general scheme, calling for the use of five separate portions, is outlined in IFig. 1. The sample is apportioned as follows, metallic phase, silica, water and carbon dioxide determinations each require a minimum of 50 mg, while major constituents, alkalies and minor conshituents require a minimum of 100 mg each. Fig. S FUSION X&CO,
(5):KK03(1)
L-----Tolume
O.OlM HCl
Cation column
i
SiO, Bulk I SiO, gra~~imetrically Residual calorimetrically
S’O, 12M HCl r
12M
Anion column
HCl
r A&.0,
The scheme of between scheme may for the main ized is fused the silica. Portion
CaO MgO
is therefore capable of giving a fairly complete analysis on a sample If the available sample is smaller, then the 300-350 mg in weight. be revised to allow determination of silica in the same portion used analysis (see Fig. 2). The residue left after the silica has been volatilwith 0.25 g of sodium carbonate and combined with the filtrate from
1: Netaltic
phase (Fe, Ni, Co)
The chemical extraction of the metallic phase by mercuric chloride was first proposed by B~SSINGAULT in 1868 and was subsequently modified by ~RIEDH~I~ (1888) to include ammonium chloride. This method has been found to be quite satisfactory provided certain conditions can be fulfilled by the sample. Where the metal particle size is >0*05 mm (i.e., about $200 sieve mesh), HABASKY (1961) has reported that the metal phase is not completely dissolved. Furthermore if the metal phase is distributed in fine particles through the silicate phase, the sample must be crushed finely enough to release these metal particles from silicate grains or at least ensure that they are exposed to the solvent solution. As far as most chondrites are concerned, crushing to -200 mesh (using the method described above) ensures complete metal extraction. Another factor to be kept~ in mind is the length of time allowed for the metal ext*raction to take place. In the course of the present study it was found that
The analysis of chord&k
meteorites
757
after 100 hours (in darkness, on a water bath) all the metal phase has been extracted. Complete extraction of metal has been established by showing that the nickel of the extracted metal phase equals the nickel content of the total chondrite sample since virtually all the nickel (and cobalt) in a normal chondrite should exist in the metal phase. In most chondrite analysis schemes (e.g., WIIK, personal communication) only iron is determined in the ext’racted solution since the presence of mercury salts interferes with nickel and cobalt determinations. Under these circumstances both nickel and cobalt are determined on the total chondrite sample and they are then recalculated as occurring only in the metallic phase. In the present scheme an anion exchange column is used to separate Fe, Ni and Co from each other and from mercuric salts. Subsequent, to this work it was found that a similar separation of Ni from Co and Fe had been employed in the analysis of copper ores and concentrates by LIBERMAN (1955). Portion 2: Xodium, potassium and minor constituents (C, Cr, Mn, Ti, P and total Fe) This portion is dissolved in sulphuric and hydrofluoric acids. The carbon is centrifuged off and the volume adjusted, the minor constituents are determined spectrophotometrically by established methods and the sodium and potassium flamephotometrically.
Oxidation of the sulphide is effected by the presence of bromine water and the slow addition of nitric acid which also brings the metal phase into solution. Hydrofluoric acid is then added to dissolve the silicate phase. After evaporation the residue is taken up in O+OlM HCl the solution passed through a cation exchange column which allows the sulphate to be elutriated while retaining the metal ions. The metal ions, i.e., R,O,, CaO and MgO are then removed from the column by 12 M HCl, and the R,O, group separated by hydroxide precipitation. The redissolved R,O, is then passed through an anion exchange column where iron, manganese, chromium and part of the titanium are held, while the aluminium is elutriated. The portion of titanium that accompanies the aluminium is complexed as a peroxide, while the aluminium is being precipitated as hydroxide. In this way aluminium is separated from the other R,O, constituents and may be determined directly. Spectrographic analysis of the ignited precipitate by GREENLAND showed titanium and chromium to be absent, therefore this is a satisfactory procedure for semi-micro work (100 mg sample). On a macro scale the larger quantities of titanium and chromium present in the solution require these to be determined on the ignited precipitate, since they are not completely held by the column or complexed during precipitation. The correction is made by fusing the ignited precipitate with potassium bisulphate and determining the chromium and titanium spectrophotomet~cally. The weight of these two oxides TiO, and Cr,O, are then subtracted from the weight of the ignited precipitate,
A. J. EASTON and J. F. LOVERING
758
After the ion exchange separation procedure had been established a paper giving a similar separation of aluminium in raw materials, sinters and slags was published (LEWIS, NARDOZZI and MELNICK, 1961). CaO and MgO may be determined gravimetrically as oxalate and pyrophosphate respectively or by E.D.T.A. titration. The normal chemical reagent blank may be run through the appropriate procedures, but using analytical reagent grade materials the only correction found necessary was for iron in the hydrochloric acid used in portion 1 for the ion exchange separation of the metallic phase. Portion 4:
Water and carbon dioxide
Water and carbon dioxide are liberated from the chondritic material by heating in a platinum boat contained within a silica tube at 1175%. The liberated vapour is flushed from the tube by a flow of dry carbon dioxide-free inert gas and is absorbed into phosphorus pentoxide and soda lime. This method allows very small quantities of water and carbon dioxide to be accurately measured on 50 mg samples. Portion
5: Silica
Where possible a separate silica determination is made combining both the gravimetrically found major portion and the spectrophotometrically determined residual silica to give a complete total silica. ANALYTICAL
Portion
SCHEME-DETAILED
PROCEDURES
1: Metallic phase (iron, nickel, cobalt)
A 50 mg minimum sample of finely powdered ( -200 mesh) chondrite is placed in a 50 ml volumetric flask together with 0.3 g of mercuric chloride and 0.3 g of ammonium chloride. 40 ml of warm water are then added and the flask rotated to assist solution of the salts. The flask is then wrapped with thin aluminium foil to exclude light and stood on a water bath for four days. The residue is separated by centrifuging, and washed several times with water to ensure that all soluble matter is collected. The combined solutions are then evaporated on a water bath to dryness and taken up in 20 ml of 10 M HCl and placed on a Dowex 1 x 4 (50-100 mesh) Anion exchange column (2 cm x 12 cm) previously prepared with 100 ml of 10 M HCl. (If an analytical grade of resin is not available then the resin is cleaned free of iron by passing 100 ml of 10 M HCl followed by 0.6 M HCI until no iron is indicated by a potassium thiocyanate test applied to the solution leaving the column. A final 100 ml of 10 M HCI is then passed through the column). The nickel is then eluted with 100 ml of 10 M HCl at the rate of 1-2 ml per minute. After collection this solution is evaporated to dryness on a water bath and taken up in a suitable volume of 1% v/v sulphuric acid, the final volume will depend upon the quantity of nickel present. The cobalt is eluted from the column with 150 ml of 6 M HCl at the rate of
The analysis of chondritic meteorites
759
1-2 ml per minute, after collection this is evaporated to dryness and taken up in a suitable quantity of water. The iron is finally eluted with 150 ml of 0.6 M HCl at the rate of l-2 ml per min. or until the elutant is found to be free from iron. The mercuric salts are retained by the resin which should be discarded after the metals have been eluted. Nickel (LIBERMAN, 1955). An aliquot or the whole solution containing up to 0.25 mg of nickel is transferred to a 100 ml flask and the volume adjusted to Sufficient bromine water (2 ml) to approximately 20 ml with distilled water. give distinct yellow colour to the solution is added, followed by 6 ml of 0.88 S.G. ammonium hydroxide and the contents of the flask thoroughly mixed by swirling. The solution is cooled below 30°C if necessary and immediately 2 ml of 1% w/v dimethylglyoxime in 95% alcohol is added to the flask and the volume adjusted to 100 ml with distilled water and thoroughly shaken. If the quantity of nickel in the aliquot is small (< 0.05 mg) a smaller final volume may be used with pro rata additions. The absorbance is measured after standing for 10 minutes out of direct sunlight, in a 1 cm cell at 455 rnp against water. The reading is referred to a calibrated curve, prepared by taking aliquots of a solution made from spectrographically pure nickel powder and treating in a similar manner. Cobalt (KLOOSTER 1921). A 10 ml aliquot containing 0.01-0.10 mg or the whole solution contained in a volume of about 10 ml is placed in a 50 ml volumetric flask. 2 ml of phospho-sulphuric acid (15 ml of concentrated sulphuric acid and 15 ml of phosphoric acid S.G. 1.7 diluted to 100 ml) is added and then 10 ml. of nitroso-R-salt (0.25% in water). After mixing, 10 ml of 50% w/v sodium acetate (hydrated) solution is added and the flask heated in a boiling water bath for 20 minutes. 5 ml of concentrated nitric acid is added and the flask heated for a further 15 minutes in the water bath. After cooling the solution is made up to volume and the absorbance measured in a 1 cm cell at 525 m,u against water. The The flask should be protected from sunlight after formation of the complex. absorbance is compared with a standard curve prepared from aliquots of a solution of “Specpure” Co,O, dissolved in a mixture of sulphuric and nitric acids. Iron (BANDEMER, SELMA and SCHAIBLE, 1944)-An aliquot containing 0.20 mg -0.25 mg is placed in a 100 ml flask, the volume is adjusted to 20 ml with distilled water and then 5 ml of 10% w/v hydroxylamine hydrochloride added and the in water solution stood aside for 5 minutes. 10 ml of 0*20/, w/v orthophenathroline and 10 ml of 10% w/v sodium citrate are added and the absorbance measured after standing for two hours in the absence of sunlight at 510 rnp in a 1 cm cell against water. The reading is referred to a calibrated curve prepared from spectrographically pure iron sponge. Portion 2: Carbon, alkalies, chromium, total iron and phosphorus
manganese, titanium,
A minimum 100 mg of split of the chondrite sample is weighed and placed in a platinum dish. All distilled water subsequently used was freed of contaminating salts by ion exchange. The powder is carefully wetted with 20 ml of distilled water and 5 ml of 150/, v/v sulphuric acid slowly added. After the reaction with the
760
A. J. EASTONand J. F. LOVERING
and sulphide has ceased 20 ml of hydrofluoric acid are added and the solution At the same time a blank is prepared using the evaporated almost to fuming. same quantities of reagents, this is mainly for use in the alkalies determinations. The solution is taken up with about 50 ml of distilled water and the carbon centrifuged off using a glass tube. The carbon residue is washed several times with water and finally with absolute alcohol, centrifuging each time to enable the clear liquid. to be decanted. The carbon is finally transferred with absolute alcohol to a weighed 10 ml platinum crucible and dried at 110°C. After being weighed on a micro balance the crucible is ignited, the loss being taken as carbon. The weight of the residue left in the crucible will indicate if chromite is present. The combined decantations are collected in a suitable volumetric flask, e.g., 100 ml and the volume adjusted with water. Chromium (VAN DER WALT and VAN DER MERWE, 1938). An aliquot containing 0.01-0.10 mg of chromium as Cr,O, is placed in a 100 ml beaker and the volume adjusted to about 20 ml. One or two drops of 1% w/v silver nitrate are added followed by 0.3 g. of ammonium persulphate. The solution is then boiled for lo-20 min. to oxidise the chromium and decompose any peroxide formed during the oxidation. When manganese is present the appearance of the permanganate colour indicates that oxidation is complete. Allow the solution to cool and neutralise by addition of sodium carbonate. Centrifuge off the precipitate which contains iron and titanium. In the absence of a centrifuge the solution may be separated The passage of the chronium solution from the precipitate by repeated decantation. after oxidation, through a filter paper causes low results due to reduction of the chromium. 15% v/v sulphuric acid is added to the centrifugate until the solution is just acidified, then 5 ml added in excess. The solution is transferred to a 50 ml volumetric flask and 10 ml of diphenylcarbazide (0.1 g in 100 ml of acetone) added, the volume is adjusted with water. Measure the absorbance as soon as possible in a 1 cm cell against water at a wavelength of 540 rnp. Compare the reading with a standard curve prepared by treating aliquots of a standard chromium solution in a similar manner. The standard chromium solution may be prepared by dissolving 0.1936 g of potassium dichromate in 1 1. of water. 10 ml of this solution diluted to 100 ml contains in each ml 0.1 mg of Cr,O,. Manganese (WILLARD and GREATHOUSE, 1917). An aliquot containing 0*05-1.2 mg of manganese as MnO is placed in a 100 ml beaker. 2.5 ml of phosphoric acid and 1 ml of concentrated sulphuric acid is added to the solution. After the addition of 0.5 g. of potassium periodate the solution is boiled for 10 min. to oxidise the manganese to permanganate. The solution is cooled to room temperature and transferred to a 50 ml volumetric flask and the volume adjusted with freshly boiled water. Measure the absorbance as soon as possible in a 1 cm cell against water at a wavelength of 525 m,u. Compare the reading with a standard curve prepared by treating aliquots of a standard manganese solution in a similar manner. The standard manganese solution may be prepared by dissolving 0.114 g of potassium permanganate in 1 1. of water containing 5 ml of 10% w/v hydroxylamine hydrochloride. 1 ml of this solution contains 0.05 mg of MnO. Titanium (EASTON and GREENLAND, 1962). In the determination of titanium metal
The analysis of chondritic meteorites
761
using tiron (YOE and ARMSTRONG, 1947), E.D.T.A. has been used to complex ferric iron (SZARVAS and CSISZAR, 1955). A modification of this method (EASTON and GREENLAND, 1962) is given where the ferric E.D.T.A. complex is reduced to the colourless ferrous complex to avoid a correction which otherwise would be of a similar order to that of the absorbance of the titanium-tiron complex required to be measured. Place an aliquot containing 0.02-0~10 mg of TiO, in a 50 ml volumetric flask. Add 5 ml of 20/b w/v aqueous solution of tiron (1: 2 dihydroxybenzene 3: 5 disulphuric acid) followed by 5 ml of 0.05 l.Mdisodium ethylenediamine tetraacetate. Add 10 ml of 1 M sodium acetate buffer and adjust the volume to 50 ml and mix well. Just prior to measurement add 50 mg of sodium dithionite and shake the flask. Measure the absorbance at a wavelength of 430 rnp in a 1 cm or 4 cm cell against water. Compare the absorbance obtained with a standard curve prepared by treating aliquots of a standard titanium solution in a similar manner. The standard titanium solution may be prepared by fusing 0.01 g of specpure titanium dioxide with 2 g of potassium bisulphate in a platinum crucible, after cooling the contents are dissolved in 3% v/v sulphuric acid by heating until a clear solution is obtained. The volume is then adjusted to 1 l., 1 ml of the solution contains 0.01 mg TiO,. Phosphorus (KITSON and MELLON, 1944). An aliquot containing O*OlO-3 mg of phosphorus as P,OB is placed in a 100 ml beaker and the volume adjusted accurately to 15 ml. 10 ml of ~anadomolybdate solution is added. The vanadomolybdate solution is prepared by dissolving 1.25 g of ammonium metavanadate in 400 ml of cool 50% v/v nitric acid. Separately dissolve 50 g of ammonium molybdate in 400 ml of water and filter off any solid particles. Add the ammonium molybdate solution to the ammonium metavanadate solution and adjust the volume to 1 1. Measure the absorbance after 5 min in a 1 cm cell against a solution prepared by the addition of 10 ml of vanadomolybdate solution to 15 ml of water at a wavelength of 430 rnp. If the phosphorus content is very low a 4 cm cell may be used. Compare the reading with a standard curve prepared by treating aliquots of a standard phosphorus solution in a similar manner. The standard phosphorous solution may be prepared by dissolving a quantity of standard phosphate rock, e.g., National Bureau of Standards phosphate rock 56b by adding 25 ml of 50% nitric acid to the weighed material in a 150 ml beaker. The beaker is covered and allowed to digest for several hours on a steam bath, until the material is dissolved. A suitable concentration is such that 1 ml of the standard solution contains 0.01 mg of phosphorus as P&l,. Alkalies. The sodium and potassium were determined on a D.U. model Beckman with a flame photometric attachment using the 589 rnp line for sodium and the 768 rnp line for potassium. An oxygen hydrogen flame was used, a minimum slit width and highest sensitivity resistor. The percentage transmission reading was bracketed by standards prepared from similar A.R. salts. The results obtained agree with those published using isotope dilution. Total iron. An aliquot is taken and the iron determined as given under metallic iron.
762
Portion 3: Sulphide,
A. J. EASTONand J. F. LOVERING Al,O,,
CaO, MgO
A 100 mg of split sample is placed in a 150 ml Pyrex beaker and covered by 40 ml of saturated bromine water and stood for 30 minutes. 5 ml of concentrated nitric acid are added slowly dropwise since any loss of H,S will result in a low The solution is set aside for several hours with occasional figure for sulphide. stirring and then evaporated on a water bath to a volume of lo-15 ml several times to expel the bromine. The solution and residue are carefully transferred to a platinum dish and 25 ml of hydrofluoric acid added and the solution evaporated to dryness on a water bath. The residue is dissolved in a few ml of dilute hydrochloric acid and distilled water; warming is usually necessary to ensure complete solution of all salts. The acidity is adjusted with dilute ammonium hydroxide until it is within the pH range 2.5-3.1. The solution is then passed through a Dowex 50 x 4 (50-100 mesh) Cation exchange column 2 cm x 7 cm previously washed with 100 ml of 0.01 M HCl. The sulphate is washed through by passing 150 ml of O-01 M HCl through the column and then precipitated from this solution by barium chloride, allowed to stand overnight and filtered off through a hardened paper and ignited in an oxidising atmosphere, the weighing being made on a micro balance. The cations after being stripped from the column by 100 ml of 12 M HCl are evaporated to dryness and subsequently taken up in dilute HCI. After a double precipitation of the R,O, group the lime and magnesia are determined either gravimetrically as the oxalate and pyrophosphate respectively or by E.D.T.A. titration using the combined R,O, filtrates. Where the lime is determined by E.D.T.A. titration (PATTON and REEDER, 1956) an aliquot of the combined filtrate is placed in a 50 ml conical flask and boiled with 5 ml of 10% w/v sodium hydroxide until ammonia is completely expelled. The flask is cooled, a few mg of potassium cyanide added, and a small quantity of Patton and Reeder’s reagent (2-hydroxy-l-(2 hydroxy-4-sulpho-1-naphthylazo)-3-naphthoic acid). The reagent is usually diluted by shaking 0.1 g with 5 g of sodium sulphate. The contents of the flask are immediately titrated with E.D.T.A. solution which has been previously standardised against a standard calcium chloride solution prepared from freshly ignited calcium carbonate. At the endpoint the pink colour changes to a clear blue. A second aliquot for the determination of magnesium is boiled with sufficient ammonium oxalate to precipitate the lime present. The excess of ammonium oxalate should be kept to the minimum. After the precipitate has settled it is filtered off and washed with water to which a few drops of ammonium hydroxide has been added. The filtrate is collected in a conical flask and 1 g of potassium bisulphate added, this replaces the ammonium chloride buffer normally used and has the advantage that a sharper endpoint is obtained. The solution is heated almost to boiling and 10 ml of 0.88 S.G. ammonium hydroxide added, and a few mg of potassium cyanide. One or two ml of solochrome black 0.4% w / v (eriochrome black) solution (0.2 g of reagent dissolved in ethyl alcohol) is added and the solution titrated with E.D.T.A. solution which has been previously standardised against a standard magnesium chloride solution prepared
The analysis of chondritic meteorites
783
At the endpoint the pink colour from freshly ignited magnesium carbonate. changes to clear blue. The R,O, group is dissolved in dilute HCl and evaporated to dryness, This step is necessary since only when using a high acid molarity, i.e., 12 M will the iron manganese, chromium and titanium be retained by the anion resin while the aluminium passes through unabsorbed. A Dowex 1 x 4 (50-100 mesh) Anion exchange column 2 x 12 cm is prepared by passing 100 mf of 12 M HCl through the column. The evaporated R,U, group is taken up in 20 ml of 12 &I HCl and The alum~n~um is then etutriated by passing a further placed on the column. 250 ml of 12 M HCl through the column, the entire solution is collected and evaporated nearly to dryness to discharge the bulk of the HCI. 5 ml of 12% w/w (40 vol.) hydrogen peroxide is added to complex any titanium which may have accompanied the aluminium due to its low absorption coefficient. The aluminium is preoipitated by the passage of gaseous ammonia through the solution and determined gravimetrically after ignition. Careful pH control is necessary for complete precipitation of the aluminium and it is preferable to add 1-2 g of solid ammonium chloride before precipitation Portion 4:
Water, carbon dioxide and carbon
The uncambined water was determined by the loss in weight of a 50 mg portion when heated for two hours at 110°C. The combined water and oarbon dioxide were determined on this dried portion using a modification of the method published by RILEY aud ~~ILLIAMS (1959). In order to avoid the possible formation of cyanogen by the action of nitrogen on the carbon present, t*his gas was replaced by argon. Due to the relatively high sulphide content an additional bubbler containing solid chromic acid in contact with syrupy phosphoric acid was placed between the water and carbon dioxide absorption tubes. This was to ensure that any sulphur compounds passing through the copper packing in the ignition tube would be trapped before the gas entered the carbon dioxide absorption tubes. A guard tube containing phosphorus pentoxide was attached to the bubbler to restrict migration of water from it into the absorption tubes, The portion of the sample which has been used to determine the uncombined water contained in a platinum boat stood in a silica boat, is loaded into the cool end of the silica combustion tube. The silica tube passes through a horizontal electric furnace. The tube is sealed and dry argon gas used to flush the tube free of atmospheric moisture and carbon dioxide. The weighed absorption tubes are then assembled, the two moisture absorption tubes containing phosphorus pentoxide, and the two carbon dioxide absorption tubes containing soda lime in the first and phosphorus pentoxide in the second. The bubbler containing chromic and phoapharic actid previously mentioned is connected between the water and carbon dioxide a’bsorption tubes and the absorption train is completed by attaching a bubbler containing concentrated sulphuric acid, as a safeguard against atmospherio contamination of the last absorption tube. The sample is then moved into the hot zone of the silica tube, usually midway in the furnace, by means of a steel rod passing through the closure of the cool end of the silica tube, The argon gas is passed for a period of 2-3 hours after which time the absorption tubes are
764
A. J. EASTONand J. F. LOVERING
disconnected and reweighed. The increase in weight in the first two absorption tubes is the weight of combined water and t’he increase in the last two absorption tubes, the weight of carbon dioxide. After completion of the determination of the combined water and carbon dioxide the argon was replaced by oxygen and the carbon ignited to carbon dioxide which was absorbed as before, in two tubes containing soda lime and This value was recalculated to give an phosphorus pentoxide respectively. additional check on the carbon content.
A 50 mg portion is fused with 2 g of sodium carbonate and potassium nitrate (5: 1) mixture in a platinum crucible, the fusion dissolved in hydrochloric acid and the silica determined gravimetrically after three separate bakings on a water bath. The ignited material is volatilised with hydrofluoric acid and the loss taken as the silica. The residual silica in solution is determined by the silica-molybdate method as given by JEFFERY and WILSO~J (1960).
Until a complete understanding of the nature of the silicate, sulphide, metal and other phases in chondrites is obtained, presentation of the analytical data must remain tentative and approximate. For instance, no attempt has been made to formulate carbides from the carbon content or sulphides other than troilite (FeS). The total iron content of the sample has been proportioned according to the general scheme used by WIIK (1956 and personal communization). Su~cient Fe is taken from the total iron content of the chondrite to combine with the S content determined from the barium sulphate precipitation on portion three and the two are then reported as the simple sulphide FeS. The iron remaining after the metallic iron (found on a separate sample) has also been deducted, is returned as FeO. When metallic iron is present only two oxidation states of iron are possible if the phases in the chondrite have formed under equilibrium conditions. Nickel, cobalt and metallic iron have been returned as components of the metal phase from which they were determined after extraction. The remaining components are returned as oxides in the states in which they normally occur in silicate rocks. It has been found that by using this method of reporting, chondritic analysis totals approximate to very nearly one hundred percent, thus confirming the general basis of the method. A typical analysis of three inclusions presented in this manner are shown in Table 1. It must at the same time be appreciated that the method does not take into account the possibility of the iron sulphide being non stoichiometric and the presence of such minerals as oldhamite (CaS), daubreelite (Fe Cr,S,) and many other phases known to be present in some chondrites. SUMMARY The scheme given above is an attempt to combine selected classical, colorimetric, flamephotometric and ion exchange procedures to give acceptable results.
The analysis Table
1. Analysis
of chondritic
of stony meteorite
inclusions
Olivine-hypersthene chondrite inclusion
Fe CO
FeS SK), TiG, Al&, CrzO3 Fe303
Fe0 MnO MgG CaO
Sa,O .3X,0 PZO, H,O’ H,Oc
* Determined
Table
2. Comparison
Peridotite
(a)
Peridotite (b) Granulite Granodiorite * Det,ermined
Table
18.77 0.27 29.02 0.99 0.42 0.11 0.34 to.10 0.30 I-02
100.39
99.06
meteorite
Aubrite inclusion
48.04 0.25 3.77 0.34 0+37* 2.85* 0.13 37.67 6.51 0.03 062 O-04 n.d
of A&O, determined by classical method exchange separation
by three independent
Ion exchange separation
and after ion
AlzG,/R,G, ratio
0,29 0.97
1:30 1:lO 1:7 1:2 3:4
1.03 16.9’7 15.30
analysts.
3. Carbon determined on carbonaceous the Bencubbin meteorke
chondrite
inclusion in
by: Port,ion 2 (residue method) Portion 4 (ignition method)
4
Carbonaceous chondrite inclusion
15.32 0.36 26.57 1.17 0.74 0.11 0.35
Classical
Aegirine
given
in the bencubbin
by classical silicate methods.
Sample
Result
765
0.92 0.91 0.037 9.37 33.05 0.14 2.98 0.42
3.98 0.87 0.038 7.84 38.91 0.11 2.86 0.35 -
Ni
meteorites
1.12%, 0.95%
l.OOC&
766
A. J. EASTONand J. F. LOVERING
Primarily the difficulties of obtaining a satisfactory aluminium result in the presence of much larger quantities of iron, chromium manganese, titanium and in the presence of phosphate have been resolved. * In Table 2 a number of results are given showing the advantage of using the ion exchange method where the Al,O, to total R,O, ratio is low. It should be mentioned that the ion exchange techniques are not tedious and are essentially simple to operate since the resins are in a sense being used as extended filtration and extraction processes. The benefits Ohat are derived from the use of the ion exchange procedures are: (a) The sulphate is precipitated in the absence of metal ions. (b) The nickel and cobalt are able to be determined on the metallic phase extract in the absence of contaminating ions. (c) The aluminium is determined without the errors due to the classical method where the R,O, group is precipitated and the aluminium found by difference. Although the mercuric-ammonium chloride extraction method has been found satisfactory when used with a finely divided metal phase present, the limitations imposed by particle size must be appreciated. The carbon determined by two different procedures on a carbonaceous chondrite inclusion are given in Table 3. A spectrophotometric determination of residual silica becomes more necessary where small quantities of sample are used for analysis since the volume of solution used, for dissolving the baked silica residue, is not always pro rata to the weight of sample and therefore the error as a percentage of the whole will be larger. Since the scheme may be used on 350 mg it is hoped that it will prove attractive for the analysis of limited samples such as minor inclusions and minerals in stony meteorites. AcknowEedgements-The authors wish to express their thanks to Mr. L. GREENLAND for helpful discussions particularly on ion exchange procedures. The authors also wish to express their thanks to Dr. H. B. WIIK for making unpublished work available to them which formed a large basis for this suggested scheme. REFERENCES BANDEMER, SELMA L. and SCHAIBLE, P. J. (1944) Determination of iron. Indust. Engng. Analyt. Chem. Ed. 16,317-319. BOSSINGAULT (1868) Analyse dune fonte chromifere dosage du carbone dans la fonte, le fer et l’acier. Paris Acad. Sci C.R. 60, 873-877. EASTON, A. J. and GREENLAND, L. (1962) The determination of titanium in meteoritic material. (In press.) FREIDHEIM, C. (1888) Uber die chemische Zusammenetzung der Meteoriten von Alfianello und Conception. S. B. Akad. Wiss. Berlin. 345-367. HABASKY, M. G. (1961) The quantitative determination of metallic iron in the presence of iron oxides in treated ores and slags.Analyt. Chem. 33, 586-588. JEFFERY, P. C. and WILSON, A. D. (1960) A combined gravimetric and photometric procedure for determining silica in silicate rocks and minerals. Analyst, 35, 1012. 478-485, KITSON, R. E. and MELLON, M. G. (1944) Calorimetric determination of phosphorus as molybdivanadophosphoric acid. Indust. and Engng. C&m. Analyt. Ed. 16, 379-383. van KLOOSTER, H. S. (1921) Nitroso R-Salt a new reagent’ for the detection of cobalt,. J. Amer. Chem. Sot. 43, 746-749. * The application of this principle to general silicate analysis is to be published elsewhere.
The analysis of chondritic meteorites
767
LEWIS, L. L., NARDOZZI, M. J. and MELINCK, L. M. (1961) Rapid chemical determination of aluminium, calcium and magnesium in raw materials, sinters and slags. Andyt. Chem. 35, 1351-1355. LIBERBUN, A. (1955) The dedication of small amounts of nickel in copper ores and concentrates containing iron and cobalt. Analyst. SO, 595-598. PATTON, J. and REEDER, W. (1956) New indicator for titration of calcium with ethylenedinitrilo tetraacetate. Analyt. Chem. 28, 1026-1028. RILEY, J. P. and WILLIAMS, H. I?. (1959) The microanalysis of silicate and carbonate minerals. Part 2. Determination of wat,er and carbon dioxide. Mikrochimiea Acta. Heft 4. SZARVAS,P. and CSISZBR,R. (1955) A&z. Chim. Hung. 7, 403. UREY, H. C. and CRAIG, II. (1953) The composition of the stone meteorites and the origin of the meteorites. Geochim. et Cosmochim. Acta. 4, 36-82. van der WALT, C. F. J. and van der MERWE (1938) Calorimetric determination of chromium in plant ash, soil, water and rocks. Analyst. 63, 8099811. WIIK, H. R. (1956) The chemical compo&ion of some stony meteorites. Geochim. et Cosmochim. Acta. 9, 279-289.
WILLARI), H. H. and GREATHOUSE,L. H. (1917) The colorimet,ric determination of manganese by oxidation with period&e. Amer. Chem. Soe. J. 39, 2366-F-2377. YOE, J. H. and ARMSTRONG,A. R. (1947) Calorimetric determination of titanium with disodiumI ,2-dihydroxybenzene-3,5disulfonate. Analyt. Chem. 19, 100-102.
Acta, 1963, \‘(A. 25, pp. $53 to ;Gi.
Pergamon PressLt,d. Printedin
Xort~hern Ireland
The analysis of chondritic meteorites A. 5. EASTOX and J. I?. LOVERIXG Department of Geophysics, Australian Kational Universit,y Canberra, A.C.T. Australia. (Received
15 September
1962; in revised fornb 11 Janwwy
1963)
Ab&&--A scheme for the analysis of chondritio material (other then volatile rich carbonaceous chondrites) is described which modifies the classical procedures by the introduction of simple ion exchange techniques. The macro constituents of the metallic phase are initially extracted with mercuric-ammonium chloride solution and then separated by elutriation from an anion exchange column. Fe, Ni and Co are then determined by spect.rometric methods without inte~erence from other ions. The al~~urn is separated by ion exchange technique from other members of the R,O, group thereby avoiding the errors of the classical method. K,O and N&,0 are determined by flamephotometry, CaO and iMgO by gravimetric methods or by E.D.T.A titration, and C is centrifuged off, weighed and ignited. Sulphide is determined as sulphate after separation from extraneous ions by ion exchange technique. H,O and CO, are determined by absorption after liberation at 1175°C.
IT HAS long been recognised that the analysis of the “normal” chondritio meteorites {i.e., those chondrites other than the carbonaceous chondrites) poses a number of special problems over and above the usual problems associated with the analysis of silicate rocks and minerals. These special problems arise from the presence of sulphide (also carbide and phosphide) and metallic phases in the chondrites along with silicate and oxide phases. Iron, in various states of oxidation, can exist in each of these phases and it is essential that any analytical scheme should be capable of making accurate determinations of the distribution of the iron content between these various phases co-exist,ing in chondritic meteorites. The analysis of the carbonaceous chondrites poses yet another set of problems because they consist of “amorphous” silicate material as well as crystalline silicates (some hydrated) and oxides (including magnet,ite) with complex mixtures of hydro~arbo~ls, water, ‘~amorphous” carbon, a number of inorganic salts (e.g., MgSO,), and undoubtedly many other materials. The difficulties surrounding the satisfactory analysis of these components are very real and, in fact no completely satisfactory analytical method has yet be devised although the best attempt so far is certainly the work of WIIK (1956). However we have made no attempt in this paper to deal with the analysis of the carbonaceous chondrites. There are over 300 analyses of stony meteorites in the literature but, in view of the difficulties involved, it is not surprising that UREY and CRAIG (1953) concluded that a considerable proportion of these analyses were unsatisfactory and 763
754
A. J.
EASTON
and
J. F. LOVERINC
must be rejected. Many of the analyses date back to the early nineteenth century but not all old analyses are necessarily incorrect. Many of the chondrite analyses carried out by G. T. PRIOR and L. H. BORSTROM over 40 years ago are generally recognised to be of high quality at the present day. The analytical scheme described here owes a great deal to the methods used and developed by WIIK who is recognised to be the most experienced analyst of chondritic meteorites at the present time. In his turn, WIIK acknowledges his indebtedness to W. A. WAHL who was the leader of the previous generation of However we should like to record our very considerable meteorite analysts. indebtedness to WINK in supplying us with details of his methods which have not yet been published. We believe that our analytical scheme for chondritic material does break new ground in that ion exchange resins are used in several steps of the scheme to separate various elements for determination without interferences from other elements. There are other features which should simplify the problems associated with the analysis of chondritic meteorites so that accurate analyses can be carried out in any modern laboratory by a competent analyst without any special previous experience. In this way it is hoped that this analytical scheme will lead to a very badly needed increase in the small number of accurate analyses of chondrites available at the present time. This analytical scheme is extremely flexible and has been used to analyse achondritic meteorites as well as all types of chondritic meteorites. SAMPLING The achondrites and the metal-poor chondrites generally present few problems as far as sampling is concerned. In these meteorites what little metal phase that does occur is generally fine grained and will generally dissolve readily in mercuric chloride-ammonium chloride solutions for subsequent analysis. However the metal-rich chondrites invariably contain large metal grains and even veins of metal which cannot be broken up by normal crushing techniques so that representative sampling becomes very difficult. Furthermore the metal aggregations in these meteorites arc too large to dissolve appreciably in mercuric chlorideammonium chloride and they cannot be separated cleanly from contaminating silicate, sulphide and other phases by any means known to us. In view of the fact that iron becomes brittle at low temperatures, R. RUDOWSKI suggested that metal-rich chondrites might be crushed finely by normal techniques provided the sample was kept near liquid air temperature. An insulated box was constructed to form a reservoir for liquid air storage and an alundum mortar (containing the chondrite sample to be crushed) and pestle was partly immersed in the liquid air through holes cut in the top of the box. After the mortar and sample had been cooled to near liquid air temperature, the metal-rich chondrite was then easily crushed to a fine powder (approximately -200 mesh). After crushing, the mortar was removed from the box and the sample was covered with acetone (to prevent condensation of ice on the sample) and then the sample was gently heated by an infra-red lamp to evaporate the acetone. Using this technique a number of quite metal-rich chondrites have been crushed to powders which pass 200 mesh sieves.
755
The analysis of chondritic meteorites
Once the original chondrite sample has been finely ground, small total sample (i.e., 300-350 mg.) is required for analysis.
only a relatively
AXALYTICAL SCHEME-GENERAL The quantity of chondritic material available for an analysis is generally limited so that it is highly desirable to arrange the analytical procedures in such a way that there is the utmost economy of sample. Even so it would seem that a minimum number of four separate portions are required for a complete analysis: (i) metallic phase, (2) alkalies and minor constituents, (3) sulphide and major Fig. 1 Portion 3.
Portion 1.
11 OXIDATION
METAL EXTRACTION
1OMHCl
Anion column
j Fe
2) E;oLUTI~N IX HF
CO
Cation column
Ni
r
12M HCl
Anion column
O.OlMHCl
so* %O, I
cao MgO
Al,O, Portion 2. SOLTTTION I?uTWFjH,SO, 1 C
CrzO,
I MnO
TiO,
I P,O,
I Total Fe
I Na,O
K,O Portion 5. FUSION Na,C0,‘5)/KN0,‘1’
Portion 4. -Hz0 +H,O CO,
I
Bulk SiO, gravimet,rically / Residual SiO, calorimetrically
constituents and (4) water, CO,. It has also been found desirable to use a fifth portion for the SiO, determination. If SiO, is determined on the same portion used for the major constituent determinations, there is a distinct possibility that incomplete removal of silica (by evaporation and baking, using the normal classical procedure) may lead to precipitation of residual silica at later stages in the analysis. Contamination of other precipitates by this residual silica can cause serious errors in the determination of various elements. In the analytical scheme proposed here a gravimetric determination of the main bulk of silica in a separate portion is followed by calorimetric determination of the residual silica in solution as proposed by JEFFERY and WILSON (1960).
A. J.
756
and J. F.
EASTON
LOVERING
The general scheme, calling for the use of five separate portions, is outlined in IFig. 1. The sample is apportioned as follows, metallic phase, silica, water and carbon dioxide determinations each require a minimum of 50 mg, while major constituents, alkalies and minor conshituents require a minimum of 100 mg each. Fig. S FUSION X&CO,
(5):KK03(1)
L-----Tolume
O.OlM HCl
Cation column
i
SiO, Bulk I SiO, gra~~imetrically Residual calorimetrically
S’O, 12M HCl r
12M
Anion column
HCl
r A&.0,
The scheme of between scheme may for the main ized is fused the silica. Portion
CaO MgO
is therefore capable of giving a fairly complete analysis on a sample If the available sample is smaller, then the 300-350 mg in weight. be revised to allow determination of silica in the same portion used analysis (see Fig. 2). The residue left after the silica has been volatilwith 0.25 g of sodium carbonate and combined with the filtrate from
1: Netaltic
phase (Fe, Ni, Co)
The chemical extraction of the metallic phase by mercuric chloride was first proposed by B~SSINGAULT in 1868 and was subsequently modified by ~RIEDH~I~ (1888) to include ammonium chloride. This method has been found to be quite satisfactory provided certain conditions can be fulfilled by the sample. Where the metal particle size is >0*05 mm (i.e., about $200 sieve mesh), HABASKY (1961) has reported that the metal phase is not completely dissolved. Furthermore if the metal phase is distributed in fine particles through the silicate phase, the sample must be crushed finely enough to release these metal particles from silicate grains or at least ensure that they are exposed to the solvent solution. As far as most chondrites are concerned, crushing to -200 mesh (using the method described above) ensures complete metal extraction. Another factor to be kept~ in mind is the length of time allowed for the metal ext*raction to take place. In the course of the present study it was found that
The analysis of chord&k
meteorites
757
after 100 hours (in darkness, on a water bath) all the metal phase has been extracted. Complete extraction of metal has been established by showing that the nickel of the extracted metal phase equals the nickel content of the total chondrite sample since virtually all the nickel (and cobalt) in a normal chondrite should exist in the metal phase. In most chondrite analysis schemes (e.g., WIIK, personal communication) only iron is determined in the ext’racted solution since the presence of mercury salts interferes with nickel and cobalt determinations. Under these circumstances both nickel and cobalt are determined on the total chondrite sample and they are then recalculated as occurring only in the metallic phase. In the present scheme an anion exchange column is used to separate Fe, Ni and Co from each other and from mercuric salts. Subsequent, to this work it was found that a similar separation of Ni from Co and Fe had been employed in the analysis of copper ores and concentrates by LIBERMAN (1955). Portion 2: Xodium, potassium and minor constituents (C, Cr, Mn, Ti, P and total Fe) This portion is dissolved in sulphuric and hydrofluoric acids. The carbon is centrifuged off and the volume adjusted, the minor constituents are determined spectrophotometrically by established methods and the sodium and potassium flamephotometrically.
Oxidation of the sulphide is effected by the presence of bromine water and the slow addition of nitric acid which also brings the metal phase into solution. Hydrofluoric acid is then added to dissolve the silicate phase. After evaporation the residue is taken up in O+OlM HCl the solution passed through a cation exchange column which allows the sulphate to be elutriated while retaining the metal ions. The metal ions, i.e., R,O,, CaO and MgO are then removed from the column by 12 M HCl, and the R,O, group separated by hydroxide precipitation. The redissolved R,O, is then passed through an anion exchange column where iron, manganese, chromium and part of the titanium are held, while the aluminium is elutriated. The portion of titanium that accompanies the aluminium is complexed as a peroxide, while the aluminium is being precipitated as hydroxide. In this way aluminium is separated from the other R,O, constituents and may be determined directly. Spectrographic analysis of the ignited precipitate by GREENLAND showed titanium and chromium to be absent, therefore this is a satisfactory procedure for semi-micro work (100 mg sample). On a macro scale the larger quantities of titanium and chromium present in the solution require these to be determined on the ignited precipitate, since they are not completely held by the column or complexed during precipitation. The correction is made by fusing the ignited precipitate with potassium bisulphate and determining the chromium and titanium spectrophotomet~cally. The weight of these two oxides TiO, and Cr,O, are then subtracted from the weight of the ignited precipitate,
A. J. EASTON and J. F. LOVERING
758
After the ion exchange separation procedure had been established a paper giving a similar separation of aluminium in raw materials, sinters and slags was published (LEWIS, NARDOZZI and MELNICK, 1961). CaO and MgO may be determined gravimetrically as oxalate and pyrophosphate respectively or by E.D.T.A. titration. The normal chemical reagent blank may be run through the appropriate procedures, but using analytical reagent grade materials the only correction found necessary was for iron in the hydrochloric acid used in portion 1 for the ion exchange separation of the metallic phase. Portion 4:
Water and carbon dioxide
Water and carbon dioxide are liberated from the chondritic material by heating in a platinum boat contained within a silica tube at 1175%. The liberated vapour is flushed from the tube by a flow of dry carbon dioxide-free inert gas and is absorbed into phosphorus pentoxide and soda lime. This method allows very small quantities of water and carbon dioxide to be accurately measured on 50 mg samples. Portion
5: Silica
Where possible a separate silica determination is made combining both the gravimetrically found major portion and the spectrophotometrically determined residual silica to give a complete total silica. ANALYTICAL
Portion
SCHEME-DETAILED
PROCEDURES
1: Metallic phase (iron, nickel, cobalt)
A 50 mg minimum sample of finely powdered ( -200 mesh) chondrite is placed in a 50 ml volumetric flask together with 0.3 g of mercuric chloride and 0.3 g of ammonium chloride. 40 ml of warm water are then added and the flask rotated to assist solution of the salts. The flask is then wrapped with thin aluminium foil to exclude light and stood on a water bath for four days. The residue is separated by centrifuging, and washed several times with water to ensure that all soluble matter is collected. The combined solutions are then evaporated on a water bath to dryness and taken up in 20 ml of 10 M HCl and placed on a Dowex 1 x 4 (50-100 mesh) Anion exchange column (2 cm x 12 cm) previously prepared with 100 ml of 10 M HCl. (If an analytical grade of resin is not available then the resin is cleaned free of iron by passing 100 ml of 10 M HCl followed by 0.6 M HCI until no iron is indicated by a potassium thiocyanate test applied to the solution leaving the column. A final 100 ml of 10 M HCI is then passed through the column). The nickel is then eluted with 100 ml of 10 M HCl at the rate of 1-2 ml per minute. After collection this solution is evaporated to dryness on a water bath and taken up in a suitable volume of 1% v/v sulphuric acid, the final volume will depend upon the quantity of nickel present. The cobalt is eluted from the column with 150 ml of 6 M HCl at the rate of
The analysis of chondritic meteorites
759
1-2 ml per minute, after collection this is evaporated to dryness and taken up in a suitable quantity of water. The iron is finally eluted with 150 ml of 0.6 M HCl at the rate of l-2 ml per min. or until the elutant is found to be free from iron. The mercuric salts are retained by the resin which should be discarded after the metals have been eluted. Nickel (LIBERMAN, 1955). An aliquot or the whole solution containing up to 0.25 mg of nickel is transferred to a 100 ml flask and the volume adjusted to Sufficient bromine water (2 ml) to approximately 20 ml with distilled water. give distinct yellow colour to the solution is added, followed by 6 ml of 0.88 S.G. ammonium hydroxide and the contents of the flask thoroughly mixed by swirling. The solution is cooled below 30°C if necessary and immediately 2 ml of 1% w/v dimethylglyoxime in 95% alcohol is added to the flask and the volume adjusted to 100 ml with distilled water and thoroughly shaken. If the quantity of nickel in the aliquot is small (< 0.05 mg) a smaller final volume may be used with pro rata additions. The absorbance is measured after standing for 10 minutes out of direct sunlight, in a 1 cm cell at 455 rnp against water. The reading is referred to a calibrated curve, prepared by taking aliquots of a solution made from spectrographically pure nickel powder and treating in a similar manner. Cobalt (KLOOSTER 1921). A 10 ml aliquot containing 0.01-0.10 mg or the whole solution contained in a volume of about 10 ml is placed in a 50 ml volumetric flask. 2 ml of phospho-sulphuric acid (15 ml of concentrated sulphuric acid and 15 ml of phosphoric acid S.G. 1.7 diluted to 100 ml) is added and then 10 ml. of nitroso-R-salt (0.25% in water). After mixing, 10 ml of 50% w/v sodium acetate (hydrated) solution is added and the flask heated in a boiling water bath for 20 minutes. 5 ml of concentrated nitric acid is added and the flask heated for a further 15 minutes in the water bath. After cooling the solution is made up to volume and the absorbance measured in a 1 cm cell at 525 m,u against water. The The flask should be protected from sunlight after formation of the complex. absorbance is compared with a standard curve prepared from aliquots of a solution of “Specpure” Co,O, dissolved in a mixture of sulphuric and nitric acids. Iron (BANDEMER, SELMA and SCHAIBLE, 1944)-An aliquot containing 0.20 mg -0.25 mg is placed in a 100 ml flask, the volume is adjusted to 20 ml with distilled water and then 5 ml of 10% w/v hydroxylamine hydrochloride added and the in water solution stood aside for 5 minutes. 10 ml of 0*20/, w/v orthophenathroline and 10 ml of 10% w/v sodium citrate are added and the absorbance measured after standing for two hours in the absence of sunlight at 510 rnp in a 1 cm cell against water. The reading is referred to a calibrated curve prepared from spectrographically pure iron sponge. Portion 2: Carbon, alkalies, chromium, total iron and phosphorus
manganese, titanium,
A minimum 100 mg of split of the chondrite sample is weighed and placed in a platinum dish. All distilled water subsequently used was freed of contaminating salts by ion exchange. The powder is carefully wetted with 20 ml of distilled water and 5 ml of 150/, v/v sulphuric acid slowly added. After the reaction with the
760
A. J. EASTONand J. F. LOVERING
and sulphide has ceased 20 ml of hydrofluoric acid are added and the solution At the same time a blank is prepared using the evaporated almost to fuming. same quantities of reagents, this is mainly for use in the alkalies determinations. The solution is taken up with about 50 ml of distilled water and the carbon centrifuged off using a glass tube. The carbon residue is washed several times with water and finally with absolute alcohol, centrifuging each time to enable the clear liquid. to be decanted. The carbon is finally transferred with absolute alcohol to a weighed 10 ml platinum crucible and dried at 110°C. After being weighed on a micro balance the crucible is ignited, the loss being taken as carbon. The weight of the residue left in the crucible will indicate if chromite is present. The combined decantations are collected in a suitable volumetric flask, e.g., 100 ml and the volume adjusted with water. Chromium (VAN DER WALT and VAN DER MERWE, 1938). An aliquot containing 0.01-0.10 mg of chromium as Cr,O, is placed in a 100 ml beaker and the volume adjusted to about 20 ml. One or two drops of 1% w/v silver nitrate are added followed by 0.3 g. of ammonium persulphate. The solution is then boiled for lo-20 min. to oxidise the chromium and decompose any peroxide formed during the oxidation. When manganese is present the appearance of the permanganate colour indicates that oxidation is complete. Allow the solution to cool and neutralise by addition of sodium carbonate. Centrifuge off the precipitate which contains iron and titanium. In the absence of a centrifuge the solution may be separated The passage of the chronium solution from the precipitate by repeated decantation. after oxidation, through a filter paper causes low results due to reduction of the chromium. 15% v/v sulphuric acid is added to the centrifugate until the solution is just acidified, then 5 ml added in excess. The solution is transferred to a 50 ml volumetric flask and 10 ml of diphenylcarbazide (0.1 g in 100 ml of acetone) added, the volume is adjusted with water. Measure the absorbance as soon as possible in a 1 cm cell against water at a wavelength of 540 rnp. Compare the reading with a standard curve prepared by treating aliquots of a standard chromium solution in a similar manner. The standard chromium solution may be prepared by dissolving 0.1936 g of potassium dichromate in 1 1. of water. 10 ml of this solution diluted to 100 ml contains in each ml 0.1 mg of Cr,O,. Manganese (WILLARD and GREATHOUSE, 1917). An aliquot containing 0*05-1.2 mg of manganese as MnO is placed in a 100 ml beaker. 2.5 ml of phosphoric acid and 1 ml of concentrated sulphuric acid is added to the solution. After the addition of 0.5 g. of potassium periodate the solution is boiled for 10 min. to oxidise the manganese to permanganate. The solution is cooled to room temperature and transferred to a 50 ml volumetric flask and the volume adjusted with freshly boiled water. Measure the absorbance as soon as possible in a 1 cm cell against water at a wavelength of 525 m,u. Compare the reading with a standard curve prepared by treating aliquots of a standard manganese solution in a similar manner. The standard manganese solution may be prepared by dissolving 0.114 g of potassium permanganate in 1 1. of water containing 5 ml of 10% w/v hydroxylamine hydrochloride. 1 ml of this solution contains 0.05 mg of MnO. Titanium (EASTON and GREENLAND, 1962). In the determination of titanium metal
The analysis of chondritic meteorites
761
using tiron (YOE and ARMSTRONG, 1947), E.D.T.A. has been used to complex ferric iron (SZARVAS and CSISZAR, 1955). A modification of this method (EASTON and GREENLAND, 1962) is given where the ferric E.D.T.A. complex is reduced to the colourless ferrous complex to avoid a correction which otherwise would be of a similar order to that of the absorbance of the titanium-tiron complex required to be measured. Place an aliquot containing 0.02-0~10 mg of TiO, in a 50 ml volumetric flask. Add 5 ml of 20/b w/v aqueous solution of tiron (1: 2 dihydroxybenzene 3: 5 disulphuric acid) followed by 5 ml of 0.05 l.Mdisodium ethylenediamine tetraacetate. Add 10 ml of 1 M sodium acetate buffer and adjust the volume to 50 ml and mix well. Just prior to measurement add 50 mg of sodium dithionite and shake the flask. Measure the absorbance at a wavelength of 430 rnp in a 1 cm or 4 cm cell against water. Compare the absorbance obtained with a standard curve prepared by treating aliquots of a standard titanium solution in a similar manner. The standard titanium solution may be prepared by fusing 0.01 g of specpure titanium dioxide with 2 g of potassium bisulphate in a platinum crucible, after cooling the contents are dissolved in 3% v/v sulphuric acid by heating until a clear solution is obtained. The volume is then adjusted to 1 l., 1 ml of the solution contains 0.01 mg TiO,. Phosphorus (KITSON and MELLON, 1944). An aliquot containing O*OlO-3 mg of phosphorus as P,OB is placed in a 100 ml beaker and the volume adjusted accurately to 15 ml. 10 ml of ~anadomolybdate solution is added. The vanadomolybdate solution is prepared by dissolving 1.25 g of ammonium metavanadate in 400 ml of cool 50% v/v nitric acid. Separately dissolve 50 g of ammonium molybdate in 400 ml of water and filter off any solid particles. Add the ammonium molybdate solution to the ammonium metavanadate solution and adjust the volume to 1 1. Measure the absorbance after 5 min in a 1 cm cell against a solution prepared by the addition of 10 ml of vanadomolybdate solution to 15 ml of water at a wavelength of 430 rnp. If the phosphorus content is very low a 4 cm cell may be used. Compare the reading with a standard curve prepared by treating aliquots of a standard phosphorus solution in a similar manner. The standard phosphorous solution may be prepared by dissolving a quantity of standard phosphate rock, e.g., National Bureau of Standards phosphate rock 56b by adding 25 ml of 50% nitric acid to the weighed material in a 150 ml beaker. The beaker is covered and allowed to digest for several hours on a steam bath, until the material is dissolved. A suitable concentration is such that 1 ml of the standard solution contains 0.01 mg of phosphorus as P&l,. Alkalies. The sodium and potassium were determined on a D.U. model Beckman with a flame photometric attachment using the 589 rnp line for sodium and the 768 rnp line for potassium. An oxygen hydrogen flame was used, a minimum slit width and highest sensitivity resistor. The percentage transmission reading was bracketed by standards prepared from similar A.R. salts. The results obtained agree with those published using isotope dilution. Total iron. An aliquot is taken and the iron determined as given under metallic iron.
762
Portion 3: Sulphide,
A. J. EASTONand J. F. LOVERING Al,O,,
CaO, MgO
A 100 mg of split sample is placed in a 150 ml Pyrex beaker and covered by 40 ml of saturated bromine water and stood for 30 minutes. 5 ml of concentrated nitric acid are added slowly dropwise since any loss of H,S will result in a low The solution is set aside for several hours with occasional figure for sulphide. stirring and then evaporated on a water bath to a volume of lo-15 ml several times to expel the bromine. The solution and residue are carefully transferred to a platinum dish and 25 ml of hydrofluoric acid added and the solution evaporated to dryness on a water bath. The residue is dissolved in a few ml of dilute hydrochloric acid and distilled water; warming is usually necessary to ensure complete solution of all salts. The acidity is adjusted with dilute ammonium hydroxide until it is within the pH range 2.5-3.1. The solution is then passed through a Dowex 50 x 4 (50-100 mesh) Cation exchange column 2 cm x 7 cm previously washed with 100 ml of 0.01 M HCl. The sulphate is washed through by passing 150 ml of O-01 M HCl through the column and then precipitated from this solution by barium chloride, allowed to stand overnight and filtered off through a hardened paper and ignited in an oxidising atmosphere, the weighing being made on a micro balance. The cations after being stripped from the column by 100 ml of 12 M HCl are evaporated to dryness and subsequently taken up in dilute HCI. After a double precipitation of the R,O, group the lime and magnesia are determined either gravimetrically as the oxalate and pyrophosphate respectively or by E.D.T.A. titration using the combined R,O, filtrates. Where the lime is determined by E.D.T.A. titration (PATTON and REEDER, 1956) an aliquot of the combined filtrate is placed in a 50 ml conical flask and boiled with 5 ml of 10% w/v sodium hydroxide until ammonia is completely expelled. The flask is cooled, a few mg of potassium cyanide added, and a small quantity of Patton and Reeder’s reagent (2-hydroxy-l-(2 hydroxy-4-sulpho-1-naphthylazo)-3-naphthoic acid). The reagent is usually diluted by shaking 0.1 g with 5 g of sodium sulphate. The contents of the flask are immediately titrated with E.D.T.A. solution which has been previously standardised against a standard calcium chloride solution prepared from freshly ignited calcium carbonate. At the endpoint the pink colour changes to a clear blue. A second aliquot for the determination of magnesium is boiled with sufficient ammonium oxalate to precipitate the lime present. The excess of ammonium oxalate should be kept to the minimum. After the precipitate has settled it is filtered off and washed with water to which a few drops of ammonium hydroxide has been added. The filtrate is collected in a conical flask and 1 g of potassium bisulphate added, this replaces the ammonium chloride buffer normally used and has the advantage that a sharper endpoint is obtained. The solution is heated almost to boiling and 10 ml of 0.88 S.G. ammonium hydroxide added, and a few mg of potassium cyanide. One or two ml of solochrome black 0.4% w / v (eriochrome black) solution (0.2 g of reagent dissolved in ethyl alcohol) is added and the solution titrated with E.D.T.A. solution which has been previously standardised against a standard magnesium chloride solution prepared
The analysis of chondritic meteorites
783
At the endpoint the pink colour from freshly ignited magnesium carbonate. changes to clear blue. The R,O, group is dissolved in dilute HCl and evaporated to dryness, This step is necessary since only when using a high acid molarity, i.e., 12 M will the iron manganese, chromium and titanium be retained by the anion resin while the aluminium passes through unabsorbed. A Dowex 1 x 4 (50-100 mesh) Anion exchange column 2 x 12 cm is prepared by passing 100 mf of 12 M HCl through the column. The evaporated R,U, group is taken up in 20 ml of 12 &I HCl and The alum~n~um is then etutriated by passing a further placed on the column. 250 ml of 12 M HCl through the column, the entire solution is collected and evaporated nearly to dryness to discharge the bulk of the HCI. 5 ml of 12% w/w (40 vol.) hydrogen peroxide is added to complex any titanium which may have accompanied the aluminium due to its low absorption coefficient. The aluminium is preoipitated by the passage of gaseous ammonia through the solution and determined gravimetrically after ignition. Careful pH control is necessary for complete precipitation of the aluminium and it is preferable to add 1-2 g of solid ammonium chloride before precipitation Portion 4:
Water, carbon dioxide and carbon
The uncambined water was determined by the loss in weight of a 50 mg portion when heated for two hours at 110°C. The combined water and oarbon dioxide were determined on this dried portion using a modification of the method published by RILEY aud ~~ILLIAMS (1959). In order to avoid the possible formation of cyanogen by the action of nitrogen on the carbon present, t*his gas was replaced by argon. Due to the relatively high sulphide content an additional bubbler containing solid chromic acid in contact with syrupy phosphoric acid was placed between the water and carbon dioxide absorption tubes. This was to ensure that any sulphur compounds passing through the copper packing in the ignition tube would be trapped before the gas entered the carbon dioxide absorption tubes. A guard tube containing phosphorus pentoxide was attached to the bubbler to restrict migration of water from it into the absorption tubes, The portion of the sample which has been used to determine the uncombined water contained in a platinum boat stood in a silica boat, is loaded into the cool end of the silica combustion tube. The silica tube passes through a horizontal electric furnace. The tube is sealed and dry argon gas used to flush the tube free of atmospheric moisture and carbon dioxide. The weighed absorption tubes are then assembled, the two moisture absorption tubes containing phosphorus pentoxide, and the two carbon dioxide absorption tubes containing soda lime in the first and phosphorus pentoxide in the second. The bubbler containing chromic and phoapharic actid previously mentioned is connected between the water and carbon dioxide a’bsorption tubes and the absorption train is completed by attaching a bubbler containing concentrated sulphuric acid, as a safeguard against atmospherio contamination of the last absorption tube. The sample is then moved into the hot zone of the silica tube, usually midway in the furnace, by means of a steel rod passing through the closure of the cool end of the silica tube, The argon gas is passed for a period of 2-3 hours after which time the absorption tubes are
764
A. J. EASTONand J. F. LOVERING
disconnected and reweighed. The increase in weight in the first two absorption tubes is the weight of combined water and t’he increase in the last two absorption tubes, the weight of carbon dioxide. After completion of the determination of the combined water and carbon dioxide the argon was replaced by oxygen and the carbon ignited to carbon dioxide which was absorbed as before, in two tubes containing soda lime and This value was recalculated to give an phosphorus pentoxide respectively. additional check on the carbon content.
A 50 mg portion is fused with 2 g of sodium carbonate and potassium nitrate (5: 1) mixture in a platinum crucible, the fusion dissolved in hydrochloric acid and the silica determined gravimetrically after three separate bakings on a water bath. The ignited material is volatilised with hydrofluoric acid and the loss taken as the silica. The residual silica in solution is determined by the silica-molybdate method as given by JEFFERY and WILSO~J (1960).
Until a complete understanding of the nature of the silicate, sulphide, metal and other phases in chondrites is obtained, presentation of the analytical data must remain tentative and approximate. For instance, no attempt has been made to formulate carbides from the carbon content or sulphides other than troilite (FeS). The total iron content of the sample has been proportioned according to the general scheme used by WIIK (1956 and personal communization). Su~cient Fe is taken from the total iron content of the chondrite to combine with the S content determined from the barium sulphate precipitation on portion three and the two are then reported as the simple sulphide FeS. The iron remaining after the metallic iron (found on a separate sample) has also been deducted, is returned as FeO. When metallic iron is present only two oxidation states of iron are possible if the phases in the chondrite have formed under equilibrium conditions. Nickel, cobalt and metallic iron have been returned as components of the metal phase from which they were determined after extraction. The remaining components are returned as oxides in the states in which they normally occur in silicate rocks. It has been found that by using this method of reporting, chondritic analysis totals approximate to very nearly one hundred percent, thus confirming the general basis of the method. A typical analysis of three inclusions presented in this manner are shown in Table 1. It must at the same time be appreciated that the method does not take into account the possibility of the iron sulphide being non stoichiometric and the presence of such minerals as oldhamite (CaS), daubreelite (Fe Cr,S,) and many other phases known to be present in some chondrites. SUMMARY The scheme given above is an attempt to combine selected classical, colorimetric, flamephotometric and ion exchange procedures to give acceptable results.
The analysis Table
1. Analysis
of chondritic
of stony meteorite
inclusions
Olivine-hypersthene chondrite inclusion
Fe CO
FeS SK), TiG, Al&, CrzO3 Fe303
Fe0 MnO MgG CaO
Sa,O .3X,0 PZO, H,O’ H,Oc
* Determined
Table
2. Comparison
Peridotite
(a)
Peridotite (b) Granulite Granodiorite * Det,ermined
Table
18.77 0.27 29.02 0.99 0.42 0.11 0.34 to.10 0.30 I-02
100.39
99.06
meteorite
Aubrite inclusion
48.04 0.25 3.77 0.34 0+37* 2.85* 0.13 37.67 6.51 0.03 062 O-04 n.d
of A&O, determined by classical method exchange separation
by three independent
Ion exchange separation
and after ion
AlzG,/R,G, ratio
0,29 0.97
1:30 1:lO 1:7 1:2 3:4
1.03 16.9’7 15.30
analysts.
3. Carbon determined on carbonaceous the Bencubbin meteorke
chondrite
inclusion in
by: Port,ion 2 (residue method) Portion 4 (ignition method)
4
Carbonaceous chondrite inclusion
15.32 0.36 26.57 1.17 0.74 0.11 0.35
Classical
Aegirine
given
in the bencubbin
by classical silicate methods.
Sample
Result
765
0.92 0.91 0.037 9.37 33.05 0.14 2.98 0.42
3.98 0.87 0.038 7.84 38.91 0.11 2.86 0.35 -
Ni
meteorites
1.12%, 0.95%
l.OOC&
766
A. J. EASTONand J. F. LOVERING
Primarily the difficulties of obtaining a satisfactory aluminium result in the presence of much larger quantities of iron, chromium manganese, titanium and in the presence of phosphate have been resolved. * In Table 2 a number of results are given showing the advantage of using the ion exchange method where the Al,O, to total R,O, ratio is low. It should be mentioned that the ion exchange techniques are not tedious and are essentially simple to operate since the resins are in a sense being used as extended filtration and extraction processes. The benefits Ohat are derived from the use of the ion exchange procedures are: (a) The sulphate is precipitated in the absence of metal ions. (b) The nickel and cobalt are able to be determined on the metallic phase extract in the absence of contaminating ions. (c) The aluminium is determined without the errors due to the classical method where the R,O, group is precipitated and the aluminium found by difference. Although the mercuric-ammonium chloride extraction method has been found satisfactory when used with a finely divided metal phase present, the limitations imposed by particle size must be appreciated. The carbon determined by two different procedures on a carbonaceous chondrite inclusion are given in Table 3. A spectrophotometric determination of residual silica becomes more necessary where small quantities of sample are used for analysis since the volume of solution used, for dissolving the baked silica residue, is not always pro rata to the weight of sample and therefore the error as a percentage of the whole will be larger. Since the scheme may be used on 350 mg it is hoped that it will prove attractive for the analysis of limited samples such as minor inclusions and minerals in stony meteorites. AcknowEedgements-The authors wish to express their thanks to Mr. L. GREENLAND for helpful discussions particularly on ion exchange procedures. The authors also wish to express their thanks to Dr. H. B. WIIK for making unpublished work available to them which formed a large basis for this suggested scheme. REFERENCES BANDEMER, SELMA L. and SCHAIBLE, P. J. (1944) Determination of iron. Indust. Engng. Analyt. Chem. Ed. 16,317-319. BOSSINGAULT (1868) Analyse dune fonte chromifere dosage du carbone dans la fonte, le fer et l’acier. Paris Acad. Sci C.R. 60, 873-877. EASTON, A. J. and GREENLAND, L. (1962) The determination of titanium in meteoritic material. (In press.) FREIDHEIM, C. (1888) Uber die chemische Zusammenetzung der Meteoriten von Alfianello und Conception. S. B. Akad. Wiss. Berlin. 345-367. HABASKY, M. G. (1961) The quantitative determination of metallic iron in the presence of iron oxides in treated ores and slags.Analyt. Chem. 33, 586-588. JEFFERY, P. C. and WILSON, A. D. (1960) A combined gravimetric and photometric procedure for determining silica in silicate rocks and minerals. Analyst, 35, 1012. 478-485, KITSON, R. E. and MELLON, M. G. (1944) Calorimetric determination of phosphorus as molybdivanadophosphoric acid. Indust. and Engng. C&m. Analyt. Ed. 16, 379-383. van KLOOSTER, H. S. (1921) Nitroso R-Salt a new reagent’ for the detection of cobalt,. J. Amer. Chem. Sot. 43, 746-749. * The application of this principle to general silicate analysis is to be published elsewhere.
The analysis of chondritic meteorites
767
LEWIS, L. L., NARDOZZI, M. J. and MELINCK, L. M. (1961) Rapid chemical determination of aluminium, calcium and magnesium in raw materials, sinters and slags. Andyt. Chem. 35, 1351-1355. LIBERBUN, A. (1955) The dedication of small amounts of nickel in copper ores and concentrates containing iron and cobalt. Analyst. SO, 595-598. PATTON, J. and REEDER, W. (1956) New indicator for titration of calcium with ethylenedinitrilo tetraacetate. Analyt. Chem. 28, 1026-1028. RILEY, J. P. and WILLIAMS, H. I?. (1959) The microanalysis of silicate and carbonate minerals. Part 2. Determination of wat,er and carbon dioxide. Mikrochimiea Acta. Heft 4. SZARVAS,P. and CSISZBR,R. (1955) A&z. Chim. Hung. 7, 403. UREY, H. C. and CRAIG, II. (1953) The composition of the stone meteorites and the origin of the meteorites. Geochim. et Cosmochim. Acta. 4, 36-82. van der WALT, C. F. J. and van der MERWE (1938) Calorimetric determination of chromium in plant ash, soil, water and rocks. Analyst. 63, 8099811. WIIK, H. R. (1956) The chemical compo&ion of some stony meteorites. Geochim. et Cosmochim. Acta. 9, 279-289.
WILLARI), H. H. and GREATHOUSE,L. H. (1917) The colorimet,ric determination of manganese by oxidation with period&e. Amer. Chem. Soe. J. 39, 2366-F-2377. YOE, J. H. and ARMSTRONG,A. R. (1947) Calorimetric determination of titanium with disodiumI ,2-dihydroxybenzene-3,5disulfonate. Analyt. Chem. 19, 100-102.