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Determination of beryllium in silicate rocks
VOL. 3 (1949)
DETERMINATION
ANALYTICA CHIMICA ACTA
OF
BERYLLJUM
IN
SILICATE
ROCKS
by Sclloolof CXcr~sl~y, U?tiversdy
E. U. SANDHLL of ~Vtn~tesofa, Mirttteafiolts,
Mima.
(U.S.A.)
In the method previously described for the determination of trace amounts of beryllium in silicates, a double fusion of the sample with sodium hydroxide was made and beryllium was then determined Auorimetrically in the filtrates with morin as reagent’. This procedure gives satisfactory results when applied to silicic rocks such as granites, but, as already pointed opt, it is not suitable for basic rocks because of the retention of beryllium by iron, magnesium, and calcium in the fusion residue. The method has now been improved so that it can be applied to basic rocks. The essential feature of the modified method is the elimination of iron, magnesium, calcium, and manganese in the following way. After the sample has been decomposed with hydrofluoric and sulphuric acids and brought into hydrochloric acid solution, mercaptoacetic (thioglycolic) acid is added, and an ammonium hydroxide precipitation is made. Aluminum and titanium, together with beryllium are thus precipitated, whereas the metals mentioned remain in solution. Ferrous iron forms a complex with mercaptoacetate which gives no precipitate with ammonia, and a separation of aluminum from iron based on this behavior has already been proposed by MAYR AND GDBAUIZR~. The ammonia precipitate is then subjected to double fusion with sodium hydroxide to bring beryllium into solution. Good recoveries of beryllium are thus obtained since the residue consists essentially only of titanium oxide and such amounts of iron as may have been coprecipitated. The results obtained in applying the proposed method to subsilicic rocks as represented by two diabases and to a synthetic solution simulating a basic rock, containing from 2 to 8 p.p.m. of added beryllium, are uniformly slightly low, the worst result corresponding to 80% recovery of beryllium. The average recovery in these samples corresponds to approximately go%. Therefore, it seems reasonable to suppose that the method will give substantially correct values when applied to typical basic rocks in which the natural beryllium content is of the order of I p.p.m. as indicated by results of the analyses of composites. Although the method was developed with basic rocks especially in mind, it is believed to be more satisfactory than the previously described method for silicic rocks when results of the best accuracy are sought. References
p.
95.
E. B.
90
PLUORIMETRIC
SANDELL
VOL.
3 (x949)
DETERMINATION
Morin is unexcelled as a reagent for the determination of trace quantities of beryllium. In the method described earlier, the fluorimetric comparison was made in ultraviolet radiation. By slight modification of conditions the comparison can as well be made in daylight, and in the interest of simpl’city this procedure is used in the present method. At a sodium hydroxide concentration of 0.3 N the limit of detectability of beryllium is 0.02-0.03 y in a volume of 20 to 25 ml when the solution is viewed axially in a 1.8 x 15 cm tube and comparison is made against a blank. The tubes are held vertically in front of a w’ndow and examined against a dark, shaded background. Even light from a cloudy sky is satisfactory . for comparisons. The sensitivity of the beryllium-morin reaction falls as the hydroxyl-ion concentration increases. For this reason the filtrate from the second sodium hydroxide fusion of the ammonia precipitate is neutralized with acid before combining it with the first filtrate prior to the fluorimetric comparison. Since the sensitivity varies with the alkalinity, the sodium hydroxide concentration must be, controlled, although reasonable variation is permissible. For example, 0.4 y of beryllium in 0.24 N sodium hydroxide solution gives a fluorescence which is approximately as strong as that of 0.45 y in 0.3 N hydroxide. Aluminum has no effect except insofar as it reduces the alkalinity of the solution by aluminate formation. For the most accurate results aluminum should be added to the standards to give a concentration which is approximately the same as in the sample solution. For most rocks it may be assumed that the aluminum oxide content is 15% and the corresponding amount of aluminum may be added to the standards. Under the conditions described in the Procedure (a o.4-aliquot of a 0.25 g sample) a rock containing 15% aluminum oxide would give a value IO to 15% high for beryllium if the standards contained no aluminum. Accordingly, no significant error will result if the percentage of aluminum oxide in the sample lies between IO and 20, as is usually the case, and the equivalent of 15% aluminum oxide is added to the standards. The specificity of the morin reaction for beryllium has already been considered3. Observations made in the course of the present work confirm previous conclusions that other elements of igneous rocks do not give rise to a fluorescence in the final solution. Special attention was given to the possible fluorescence of scandium, which it was feared might find its way into the final solution in the present method. However, even when pyrophosphate (which greatly decreases the fluorescence of scandium) was omitted, there was no error (Nos. g and IO, Table I) and it may be concluded that no appreciable amount of this element escapes separation, whether in a basic rock or in a typical granite. The use of pyrophosphate in the procedure is probably not necessary, because virtually identical results were obtained in the analysis of some haif-dozen rocks whether or not it was present. However, pyrophosphate is added as a precautionary measure to prevent any Rcjeverzccs
p.
95.
VOL. 3 (1949)
DETERMINATION
OF BERYLLIUM
_-TABLE DETERMINATItiN
OT
Sample
I
_ IN
SILICATE
ROCKS
T-
Be Present
-i NO
BERYLLIUM
91
Original
Added
Total
P.p.m.
P.p.m.
-P.p.m.
-I-
Be Found
First Fusion .P.p.m.
Second Fusion -P.p.m.
Total P.p.m.
Perccntagc RCcovcry
% I 2
3 z 6 : 9 IO
Synthetic
solution’.
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-
0
-
0
2
2
0
2
2
0
2
2
0
4 4
4 4 4 8
0 0
. . . .
SynChctic solution + I G y SC Grnnitc A3 + 0.006 “,& SC .
0 0
3.5
12
Dinhnsc
A‘
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El0 .
,*
21
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13 24 15 16 27 18 IQ
;: 0 0
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4 ;: 8
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0
0
0
I.5 I.25 -
0.25
3-G 3-o -
0.3 o-75 -
5.5 -
* -5 -
=*75 1.65 1.8 3.9 3.75 4-o 7 0 3.0 3.0 3.0
7-o I.3 -
0.5 0.5 -
0.4 -
1.1
2:;: 2.0 o-7 3.8 -
o-5 o-4 I.0 -
7.5 -
o-5 -
0.5
::z x.8 5.6 8.9 2.5
ii 83 90 98 94 LOO
88 -
I.1
95 88 -
4.8 5.0 8.0 7.5
93 98 86 80
Composition in mg: 48 Al,O,, 38 Fc,O,. 25 iVg0, 25 CaO, o.G MnO, 3 TiO2, 1.2 P,O,, corrcspondmg to 19 (y, Al,O,, 15 O/ Fc,O,, IO o/o MgO, IO o/0 CaO. 0.25 o/o MnO. 1.2 o/0 TlO,. and 0.5 y’ P,O,. l~nsccl on 0.25 g snmplc of rock. Solution cvaporatcd with sulphuric and hydrofluoric acids. Calcium omitted. Pcrccntage composition : SiO, 7~ .2, Al102 15.0, Fc20, 0.7, FcO 1.5, MgO 0.8, CaO 1.8, NasO 3.6, I<:,0 4.G. TiO, 0.3, P,O, 0.07. &In0 0.01. Perccntagc composition: SiO, 7G.8. Al,O, 13.2, Fc,O, 0.3, Fe0 0.4, hIg0 0.2. CnO 0.7, Na20 3.8. IGO 4.5, TrO, 0.1. P,O, 0.02, MnO 0.05. Pcrccntagc composition. SrO, 52.7, A1202 x4.5, I%,02 7.4# FcO s.G, ;LlgO 3.7, CaO 8.0, Na,O 3.2. I<,0 I .I, TiO, I .S. P,O, 0,,25, hln0 0.24, Cu 0.024. Pcrccntagc composition: SIO, .lG.g, Al,O, 21.0. Fc,O, 3.3, FcO 5.6. h1&0 4.7, CnO 11.2. Nn,O 2.5. Ii20 0.3. TiO, x.x, P,O, 0.15, i\InO 0.12.
that would result in the unlikely event that an appreciable amount of scandium should be present in the final solution. Zinc does not give a fluorescence with morin in daylight, at least not in small quantities ( No. 12). Since the strength of the fluorescence of the beryllium-morin mixture slowly decreases on standing, standards should be prepared at the same time as the sample. The fluorescence intensity remains more constant at higher morin concentrations. fluorescence
References
p. 95.
92
E.B.
SANDELL
VOL.
3 (1949)
At least 0.02 Y0 Cr,O, may be present in the sample. If much chromium (as chromate) is present in the final solution, results will be low because of absorption of ultraviolet radiation. In such a case it may be expected that satisfactory results can be obtained by reducing chromate in the sodium hydroxide leach before filtration, but this point has not been specifically investigated. SPECIAL
SOLUTIONS
Mercafitoacetic acid, at least 80% strength. Wash solution. Dilute IO ml of concentrated hydrochloric acid and IO ml of concentrated ammonium hydroxide to I liter with water. Shortly before use, add 2 ml of mercaptoacetic acid which has been neutralized with ammonia to xoo ml of this solution. Sodium +yro@os+hate, saturated solution in water at room temperature. Filter to remove any suspended material. Methyl orange indicator solution, 0.01%. Dilute the usual laboratory solution (0.1%) ten times with water. Sodium hydroxide, 3.0 g in xoo ml of solution. Sodium cl&Z&de solution (for addition to standards to make the composition the same as the sample solution.) Dissolve 3 g of sodium hydroxide in about 50 ml of water, add I ml of methyl orange solution, and neutralize with I : I hydrochloric acid, making the final adjustment with the sodium hydroxide solution if necessary, and dilute to IOO ml with water. Aluminum sulplzate, 0.05 g of Al,O, per ml. Dissolve 32.6 g of Al,(S0,),.18H,0 in water containing 2 ml of 6 N sulphuric acid and dilute to IOO ml. Filter if not 0.5 ml with 5 ml of entirely clear. Test the solution for beryllium by treating sodium hydroxide and 5 ml of sodium pyrophosphatc, diluting to 20 ml, adding 0.2 ml of morin, and comparing against a similar blank solution. The fluorescence, if any, should be less than that of 0.05 y of beryllium in the comparison solution. Morin, 0.05 %. Dissolve 50 mg of solid in IOO ml of reagent-grade acetone. Standard ljeryllium solution, O.OOI%, or a lower concentration if preferred, in 0.2 N hydrochloric acid. Air-dried recrystallized beryllium sulphate tetrahydrate may be used as the source of beryllium (BeSO,.4H.#/Be = 19.7). PllOCBDURE
Add 2 ml of 6 N sulphuric acid and 3 ml of hydrofluoric acid to 0.25 g of IOOmesh rock sample in a platinum dish or crucible. Evaporate to dryness on a hot plate and raise the temperature to expel the excess of sulphuric acid. Add 0.5 ml of 6 N sulphuric acid and a few milliliters of water, evaporate to dryness, and again drive off the free sulphuric acid. Treat the residue with 2 ml of concentrated hydrochloric acid and 20 ml of water and heat near the boiling point with stirring Rcferwrces p. 95.
WC
3 (1949)
DETERMINATION
OF
BERYLLIUM
93
until complete or almost complete solution has been obtained. A turbidity due to barium sulphate or a small residue of quartz may be disregarded. Most of any insoluble material will be decomposed in the sodium hydroxide fusion to follow, but if there is reason to believe that appreciable amounts of minerals resistant to such treatment remain, the residue should be given appropriate treatment. Transfer the solution to a small beaker. Ammonia precipitation. Add I : I ammonium hydroxide to the cold solution until a faint permanent precipitate is obtained and bring it into solution by the addition of a drop or two of hydrochloric acid. Heat to boiling. Disregard any precipitate formed on heating. Next add 2.5 ml of mercaptoacetic acid and then I : I ammonium hydroxide until a slight excess is present as indicated by odor or by spotting the solution on phenol red paper (distinct red color). Keep the mixture near the boiling point for a few minutes and the filter through a g cm paper of medium or coarse texture. Wash the precipitate with four 3 ml portions of hot wash solution and once with water. When much iron is present in the sample, the washed precipitate may not be entirely white, but this does not matter. Open the filter paper and allow it to dry in the air overnight. Carefully scrape the dried precipitate from the paper with a spatula and transfer to a nickel crucible. Any small amount of precipitate remaining adhering to the paper may usually be neglected in the case of basic rocks with low beryllium contents. With silicic rocks it is safest to ignite (in platinum) the paper from which most of the precipitate has been removed and to add the ash to the nickel crucible. Sodium hydroxide fzcsiou. Add 0.75 g (5 pellets) of sodium hydroxide to the nickel crucible. It is advisable to weigh the 5 pellets of sodium hydroxide rapidly to bc certain that the weight is within 10% of 0.75 g. If the difference is greater, allowance for the variation should be made later by adding a corresponding amount of sodium hydroxide to the standards. Heat gently at first to the fusion point of sodium hydroxide, keep at this temperature for a few minutes, and then heat to medium redness. Keep at the latter temperature for IO minutes. Swirl the melt while it is cooling so that it will solidify as a shell on the walls of the crucible. When the contents are cold, add 13 ml of water and 2 or 3 drops of ethyl alcohol to reduce any manganate which may be present. Allow to stand for 15 to 3ominutes after the sodium hydroxide has dissolved. Transfer the solution to a small beaker. Filter through a small (5 cm) retentive filter paper. It is best to refilter the first few millimeters of the solution to be certain that an entirely clear filtrate will be obtained. Catch the filtrate in a 50 ml volumetric flask. Wash with small portions of cold water totaling 8 or g ml. Ignite the paper and its contents (best in a platinum crucible) and fuse the residue in a nickel crucible as before with 5 pellets of sodium hydroxide. Extract the melt with water, filter, and wash as already described, but collect the filtrate and washings in a small beaker. Add 0.1 ml of methyl orange solution and neutralize with I : I hydrochloric acid. Combine the Refermaces p. 95.
E.B.
94
SANDELL
VOL.
3 (1949)
neutralized solution with the solution in the volumetric flask and dilute to the mark with water. Fluorimelric comfiarison. Transfer 20 ml of the mixed solution to a 1.8 x 15 cm glass-stoppered flat-bottomed tube (capacity slightly greater than 25 ml) and add 5 ml of sodium pyrophosphatc solution. Prepare a series of standards by taking IO ml of sodium chloride solution, the volume of aluminum solution to furnish the amount of aluminum present in the 2/5 aliquot of the sample (in most cases it suffices to assume that the alumina content of the rock is IS’$/~and to add the corresponding amount of aluminum to the standards), IO ml of sodium hydroxide (or slightly different volume if the amount of sodium hydroxide in the sample aliquot is not exactly 0.3 g), 5 ml of sodium pyrophosphate solution, and suitable amounts of beryllium. For basic rocks the series o, 0.05, 0.1 and 0.15 y of beryllium is suggested, and for acidic rocks the series 0.1, 0.2, 0.3 and 0.4 y. Add 0.20 ml of morin solution to each tube and mix by inversion. Remove the stoppers and compare the fluorescences by examining the tubes axially in strong daylight against a dark background. If desired the approximate beryllium content of the aliquot can first be obtained by adding standard beryllium solution to a comparison tube until the fluorescence matches that of the sample tube. Then the final comparison is made by using a fresh aliquot and a series of standards, the number of which can now be small. If the beryllium content of the sample is 3 p.p.m. and greater, a IO ml aliquot is sufficiently large; the volume of the final solution should then be increased to 20-25 ml by dilution with water. SUMMARY An rmprovcd method for the dctcrminatron of traces of beryllium in sihcatc rocks is dcscribed, which can bc applied to subsilicrc as well as silicic types. BBcryllrum is scparatcd, togcthcr with aluminum, from calcium, mngncsium, mnngancsc, and iron by ammonia prccipitatron in Lhc prcscncc of mcrcaptoacctic acid to keep Iron in solution. The beryllium in the precipitate is brought into solution, and scparatcd from trtanium and small amounts of iron, and possibly other coprccipitatcd metals, by double fusion with sodium hydroxide. The final determination of beryllium is made fluorimctrically with morin.
L’autcur dfxrit unc mbthodc pour doscr les traces dc glucinium dans lcs rochcs silicat&es. pouvant Btrc appliqubc h divers silicates. Lc glucinium cst &par&, cn m&mc tcmps quc l’alummium, du calcium, du magn&sium, du mangan&sc et du fcr, par l’nmmoniaquc, cn prQencc d’acitlc thioglycoliquc pour maintenir le fcr cn solution. Lc glucinium pr6cipit6 cst mis cn solution ct. s&par& du titane, dc traces dc fcr ct bvcntucllemcnt d’autrcs mbtaux coprbciprt&s par cloublc fusion avcc l’hydroxydc dc soclium. On dose finalcmcnt Ic glucinium par fluorimktric, cn utilisant la morinc commc rCactif. ZUSAMMENFASSUNG Dcr Verfasscr bcschreibt cinc Mcthodc zur Bcstimmung felscn. wclchc auf vcrschrcdcne Silikatc angcwandt wcrdcn Refevcmes
p. 95.
von Bcrylliumspurcn in Silikatkann. Beryllium wird zusammen
VOL. 3 (1949)
DETERMINATION
OF
95
BERYLLIUM
xnit Aluminium, van Kalzium. Magnesium, Mnngan und Eiscn mit Hilfc von Ammoniak abgcdnmit das Eiscn fliissig gchaltcn schieden, und zwar in Gegenwart von Thioglykollsiiurc, wcrden kann. Das gcfklltc Beryllium wird in L&sung gebracht und vom Titan und von Elscnspuren sowic cventucll von nndcren mitgcf&lltcn Mctallen durch Doppclschmclzung mlt Natriumhydroxyd gctrcnnt. DIG endgiiltigc Bcstimmung dcs Berylliums geschrcht auf fluorimctrischcm Wcgc untcr Anwcndung von Morin als Rcagcnsmittcl. REFERENCES 1 E. B. SANDIILL. 1mY. IZ:ng.Chewa., AtmZ. Ed., 12 (1940) 67.4. 2%. MAYR AND A. GEBAUER, Z. arlaf.Cirern.. x13 (1938) 200. 0 E. B. SANDELL, Ittd. Eng. Chctn., Atud. Ed., 12 (1940) 762.
Received April 26th, 1948
DETERMINATION
ANALYTICA CHIMICA ACTA
OF
BERYLLJUM
IN
SILICATE
ROCKS
by Sclloolof CXcr~sl~y, U?tiversdy
E. U. SANDHLL of ~Vtn~tesofa, Mirttteafiolts,
Mima.
(U.S.A.)
In the method previously described for the determination of trace amounts of beryllium in silicates, a double fusion of the sample with sodium hydroxide was made and beryllium was then determined Auorimetrically in the filtrates with morin as reagent’. This procedure gives satisfactory results when applied to silicic rocks such as granites, but, as already pointed opt, it is not suitable for basic rocks because of the retention of beryllium by iron, magnesium, and calcium in the fusion residue. The method has now been improved so that it can be applied to basic rocks. The essential feature of the modified method is the elimination of iron, magnesium, calcium, and manganese in the following way. After the sample has been decomposed with hydrofluoric and sulphuric acids and brought into hydrochloric acid solution, mercaptoacetic (thioglycolic) acid is added, and an ammonium hydroxide precipitation is made. Aluminum and titanium, together with beryllium are thus precipitated, whereas the metals mentioned remain in solution. Ferrous iron forms a complex with mercaptoacetate which gives no precipitate with ammonia, and a separation of aluminum from iron based on this behavior has already been proposed by MAYR AND GDBAUIZR~. The ammonia precipitate is then subjected to double fusion with sodium hydroxide to bring beryllium into solution. Good recoveries of beryllium are thus obtained since the residue consists essentially only of titanium oxide and such amounts of iron as may have been coprecipitated. The results obtained in applying the proposed method to subsilicic rocks as represented by two diabases and to a synthetic solution simulating a basic rock, containing from 2 to 8 p.p.m. of added beryllium, are uniformly slightly low, the worst result corresponding to 80% recovery of beryllium. The average recovery in these samples corresponds to approximately go%. Therefore, it seems reasonable to suppose that the method will give substantially correct values when applied to typical basic rocks in which the natural beryllium content is of the order of I p.p.m. as indicated by results of the analyses of composites. Although the method was developed with basic rocks especially in mind, it is believed to be more satisfactory than the previously described method for silicic rocks when results of the best accuracy are sought. References
p.
95.
E. B.
90
PLUORIMETRIC
SANDELL
VOL.
3 (x949)
DETERMINATION
Morin is unexcelled as a reagent for the determination of trace quantities of beryllium. In the method described earlier, the fluorimetric comparison was made in ultraviolet radiation. By slight modification of conditions the comparison can as well be made in daylight, and in the interest of simpl’city this procedure is used in the present method. At a sodium hydroxide concentration of 0.3 N the limit of detectability of beryllium is 0.02-0.03 y in a volume of 20 to 25 ml when the solution is viewed axially in a 1.8 x 15 cm tube and comparison is made against a blank. The tubes are held vertically in front of a w’ndow and examined against a dark, shaded background. Even light from a cloudy sky is satisfactory . for comparisons. The sensitivity of the beryllium-morin reaction falls as the hydroxyl-ion concentration increases. For this reason the filtrate from the second sodium hydroxide fusion of the ammonia precipitate is neutralized with acid before combining it with the first filtrate prior to the fluorimetric comparison. Since the sensitivity varies with the alkalinity, the sodium hydroxide concentration must be, controlled, although reasonable variation is permissible. For example, 0.4 y of beryllium in 0.24 N sodium hydroxide solution gives a fluorescence which is approximately as strong as that of 0.45 y in 0.3 N hydroxide. Aluminum has no effect except insofar as it reduces the alkalinity of the solution by aluminate formation. For the most accurate results aluminum should be added to the standards to give a concentration which is approximately the same as in the sample solution. For most rocks it may be assumed that the aluminum oxide content is 15% and the corresponding amount of aluminum may be added to the standards. Under the conditions described in the Procedure (a o.4-aliquot of a 0.25 g sample) a rock containing 15% aluminum oxide would give a value IO to 15% high for beryllium if the standards contained no aluminum. Accordingly, no significant error will result if the percentage of aluminum oxide in the sample lies between IO and 20, as is usually the case, and the equivalent of 15% aluminum oxide is added to the standards. The specificity of the morin reaction for beryllium has already been considered3. Observations made in the course of the present work confirm previous conclusions that other elements of igneous rocks do not give rise to a fluorescence in the final solution. Special attention was given to the possible fluorescence of scandium, which it was feared might find its way into the final solution in the present method. However, even when pyrophosphate (which greatly decreases the fluorescence of scandium) was omitted, there was no error (Nos. g and IO, Table I) and it may be concluded that no appreciable amount of this element escapes separation, whether in a basic rock or in a typical granite. The use of pyrophosphate in the procedure is probably not necessary, because virtually identical results were obtained in the analysis of some haif-dozen rocks whether or not it was present. However, pyrophosphate is added as a precautionary measure to prevent any Rcjeverzccs
p.
95.
VOL. 3 (1949)
DETERMINATION
OF BERYLLIUM
_-TABLE DETERMINATItiN
OT
Sample
I
_ IN
SILICATE
ROCKS
T-
Be Present
-i NO
BERYLLIUM
91
Original
Added
Total
P.p.m.
P.p.m.
-P.p.m.
-I-
Be Found
First Fusion .P.p.m.
Second Fusion -P.p.m.
Total P.p.m.
Perccntagc RCcovcry
% I 2
3 z 6 : 9 IO
Synthetic
solution’.
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-
0
-
0
2
2
0
2
2
0
2
2
0
4 4
4 4 4 8
0 0
. . . .
SynChctic solution + I G y SC Grnnitc A3 + 0.006 “,& SC .
0 0
3.5
12
Dinhnsc
A‘
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21
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20
23
0
3.5
0
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13 24 15 16 27 18 IQ
;: 0 0
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0 0 0 0 ;: 0 0
4 ;: 8
;:; 5.8 9.8 1.8 5.x 5.1 9.1 9-r
0
0
0
I.5 I.25 -
0.25
3-G 3-o -
0.3 o-75 -
5.5 -
* -5 -
=*75 1.65 1.8 3.9 3.75 4-o 7 0 3.0 3.0 3.0
7-o I.3 -
0.5 0.5 -
0.4 -
1.1
2:;: 2.0 o-7 3.8 -
o-5 o-4 I.0 -
7.5 -
o-5 -
0.5
::z x.8 5.6 8.9 2.5
ii 83 90 98 94 LOO
88 -
I.1
95 88 -
4.8 5.0 8.0 7.5
93 98 86 80
Composition in mg: 48 Al,O,, 38 Fc,O,. 25 iVg0, 25 CaO, o.G MnO, 3 TiO2, 1.2 P,O,, corrcspondmg to 19 (y, Al,O,, 15 O/ Fc,O,, IO o/o MgO, IO o/0 CaO. 0.25 o/o MnO. 1.2 o/0 TlO,. and 0.5 y’ P,O,. l~nsccl on 0.25 g snmplc of rock. Solution cvaporatcd with sulphuric and hydrofluoric acids. Calcium omitted. Pcrccntage composition : SiO, 7~ .2, Al102 15.0, Fc20, 0.7, FcO 1.5, MgO 0.8, CaO 1.8, NasO 3.6, I<:,0 4.G. TiO, 0.3, P,O, 0.07. &In0 0.01. Perccntagc composition: SiO, 7G.8. Al,O, 13.2, Fc,O, 0.3, Fe0 0.4, hIg0 0.2. CnO 0.7, Na20 3.8. IGO 4.5, TrO, 0.1. P,O, 0.02, MnO 0.05. Pcrccntagc composition. SrO, 52.7, A1202 x4.5, I%,02 7.4# FcO s.G, ;LlgO 3.7, CaO 8.0, Na,O 3.2. I<,0 I .I, TiO, I .S. P,O, 0,,25, hln0 0.24, Cu 0.024. Pcrccntagc composition: SIO, .lG.g, Al,O, 21.0. Fc,O, 3.3, FcO 5.6. h1&0 4.7, CnO 11.2. Nn,O 2.5. Ii20 0.3. TiO, x.x, P,O, 0.15, i\InO 0.12.
that would result in the unlikely event that an appreciable amount of scandium should be present in the final solution. Zinc does not give a fluorescence with morin in daylight, at least not in small quantities ( No. 12). Since the strength of the fluorescence of the beryllium-morin mixture slowly decreases on standing, standards should be prepared at the same time as the sample. The fluorescence intensity remains more constant at higher morin concentrations. fluorescence
References
p. 95.
92
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At least 0.02 Y0 Cr,O, may be present in the sample. If much chromium (as chromate) is present in the final solution, results will be low because of absorption of ultraviolet radiation. In such a case it may be expected that satisfactory results can be obtained by reducing chromate in the sodium hydroxide leach before filtration, but this point has not been specifically investigated. SPECIAL
SOLUTIONS
Mercafitoacetic acid, at least 80% strength. Wash solution. Dilute IO ml of concentrated hydrochloric acid and IO ml of concentrated ammonium hydroxide to I liter with water. Shortly before use, add 2 ml of mercaptoacetic acid which has been neutralized with ammonia to xoo ml of this solution. Sodium +yro@os+hate, saturated solution in water at room temperature. Filter to remove any suspended material. Methyl orange indicator solution, 0.01%. Dilute the usual laboratory solution (0.1%) ten times with water. Sodium hydroxide, 3.0 g in xoo ml of solution. Sodium cl&Z&de solution (for addition to standards to make the composition the same as the sample solution.) Dissolve 3 g of sodium hydroxide in about 50 ml of water, add I ml of methyl orange solution, and neutralize with I : I hydrochloric acid, making the final adjustment with the sodium hydroxide solution if necessary, and dilute to IOO ml with water. Aluminum sulplzate, 0.05 g of Al,O, per ml. Dissolve 32.6 g of Al,(S0,),.18H,0 in water containing 2 ml of 6 N sulphuric acid and dilute to IOO ml. Filter if not 0.5 ml with 5 ml of entirely clear. Test the solution for beryllium by treating sodium hydroxide and 5 ml of sodium pyrophosphatc, diluting to 20 ml, adding 0.2 ml of morin, and comparing against a similar blank solution. The fluorescence, if any, should be less than that of 0.05 y of beryllium in the comparison solution. Morin, 0.05 %. Dissolve 50 mg of solid in IOO ml of reagent-grade acetone. Standard ljeryllium solution, O.OOI%, or a lower concentration if preferred, in 0.2 N hydrochloric acid. Air-dried recrystallized beryllium sulphate tetrahydrate may be used as the source of beryllium (BeSO,.4H.#/Be = 19.7). PllOCBDURE
Add 2 ml of 6 N sulphuric acid and 3 ml of hydrofluoric acid to 0.25 g of IOOmesh rock sample in a platinum dish or crucible. Evaporate to dryness on a hot plate and raise the temperature to expel the excess of sulphuric acid. Add 0.5 ml of 6 N sulphuric acid and a few milliliters of water, evaporate to dryness, and again drive off the free sulphuric acid. Treat the residue with 2 ml of concentrated hydrochloric acid and 20 ml of water and heat near the boiling point with stirring Rcferwrces p. 95.
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DETERMINATION
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93
until complete or almost complete solution has been obtained. A turbidity due to barium sulphate or a small residue of quartz may be disregarded. Most of any insoluble material will be decomposed in the sodium hydroxide fusion to follow, but if there is reason to believe that appreciable amounts of minerals resistant to such treatment remain, the residue should be given appropriate treatment. Transfer the solution to a small beaker. Ammonia precipitation. Add I : I ammonium hydroxide to the cold solution until a faint permanent precipitate is obtained and bring it into solution by the addition of a drop or two of hydrochloric acid. Heat to boiling. Disregard any precipitate formed on heating. Next add 2.5 ml of mercaptoacetic acid and then I : I ammonium hydroxide until a slight excess is present as indicated by odor or by spotting the solution on phenol red paper (distinct red color). Keep the mixture near the boiling point for a few minutes and the filter through a g cm paper of medium or coarse texture. Wash the precipitate with four 3 ml portions of hot wash solution and once with water. When much iron is present in the sample, the washed precipitate may not be entirely white, but this does not matter. Open the filter paper and allow it to dry in the air overnight. Carefully scrape the dried precipitate from the paper with a spatula and transfer to a nickel crucible. Any small amount of precipitate remaining adhering to the paper may usually be neglected in the case of basic rocks with low beryllium contents. With silicic rocks it is safest to ignite (in platinum) the paper from which most of the precipitate has been removed and to add the ash to the nickel crucible. Sodium hydroxide fzcsiou. Add 0.75 g (5 pellets) of sodium hydroxide to the nickel crucible. It is advisable to weigh the 5 pellets of sodium hydroxide rapidly to bc certain that the weight is within 10% of 0.75 g. If the difference is greater, allowance for the variation should be made later by adding a corresponding amount of sodium hydroxide to the standards. Heat gently at first to the fusion point of sodium hydroxide, keep at this temperature for a few minutes, and then heat to medium redness. Keep at the latter temperature for IO minutes. Swirl the melt while it is cooling so that it will solidify as a shell on the walls of the crucible. When the contents are cold, add 13 ml of water and 2 or 3 drops of ethyl alcohol to reduce any manganate which may be present. Allow to stand for 15 to 3ominutes after the sodium hydroxide has dissolved. Transfer the solution to a small beaker. Filter through a small (5 cm) retentive filter paper. It is best to refilter the first few millimeters of the solution to be certain that an entirely clear filtrate will be obtained. Catch the filtrate in a 50 ml volumetric flask. Wash with small portions of cold water totaling 8 or g ml. Ignite the paper and its contents (best in a platinum crucible) and fuse the residue in a nickel crucible as before with 5 pellets of sodium hydroxide. Extract the melt with water, filter, and wash as already described, but collect the filtrate and washings in a small beaker. Add 0.1 ml of methyl orange solution and neutralize with I : I hydrochloric acid. Combine the Refermaces p. 95.
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neutralized solution with the solution in the volumetric flask and dilute to the mark with water. Fluorimelric comfiarison. Transfer 20 ml of the mixed solution to a 1.8 x 15 cm glass-stoppered flat-bottomed tube (capacity slightly greater than 25 ml) and add 5 ml of sodium pyrophosphatc solution. Prepare a series of standards by taking IO ml of sodium chloride solution, the volume of aluminum solution to furnish the amount of aluminum present in the 2/5 aliquot of the sample (in most cases it suffices to assume that the alumina content of the rock is IS’$/~and to add the corresponding amount of aluminum to the standards), IO ml of sodium hydroxide (or slightly different volume if the amount of sodium hydroxide in the sample aliquot is not exactly 0.3 g), 5 ml of sodium pyrophosphate solution, and suitable amounts of beryllium. For basic rocks the series o, 0.05, 0.1 and 0.15 y of beryllium is suggested, and for acidic rocks the series 0.1, 0.2, 0.3 and 0.4 y. Add 0.20 ml of morin solution to each tube and mix by inversion. Remove the stoppers and compare the fluorescences by examining the tubes axially in strong daylight against a dark background. If desired the approximate beryllium content of the aliquot can first be obtained by adding standard beryllium solution to a comparison tube until the fluorescence matches that of the sample tube. Then the final comparison is made by using a fresh aliquot and a series of standards, the number of which can now be small. If the beryllium content of the sample is 3 p.p.m. and greater, a IO ml aliquot is sufficiently large; the volume of the final solution should then be increased to 20-25 ml by dilution with water. SUMMARY An rmprovcd method for the dctcrminatron of traces of beryllium in sihcatc rocks is dcscribed, which can bc applied to subsilicrc as well as silicic types. BBcryllrum is scparatcd, togcthcr with aluminum, from calcium, mngncsium, mnngancsc, and iron by ammonia prccipitatron in Lhc prcscncc of mcrcaptoacctic acid to keep Iron in solution. The beryllium in the precipitate is brought into solution, and scparatcd from trtanium and small amounts of iron, and possibly other coprccipitatcd metals, by double fusion with sodium hydroxide. The final determination of beryllium is made fluorimctrically with morin.
L’autcur dfxrit unc mbthodc pour doscr les traces dc glucinium dans lcs rochcs silicat&es. pouvant Btrc appliqubc h divers silicates. Lc glucinium cst &par&, cn m&mc tcmps quc l’alummium, du calcium, du magn&sium, du mangan&sc et du fcr, par l’nmmoniaquc, cn prQencc d’acitlc thioglycoliquc pour maintenir le fcr cn solution. Lc glucinium pr6cipit6 cst mis cn solution ct. s&par& du titane, dc traces dc fcr ct bvcntucllemcnt d’autrcs mbtaux coprbciprt&s par cloublc fusion avcc l’hydroxydc dc soclium. On dose finalcmcnt Ic glucinium par fluorimktric, cn utilisant la morinc commc rCactif. ZUSAMMENFASSUNG Dcr Verfasscr bcschreibt cinc Mcthodc zur Bcstimmung felscn. wclchc auf vcrschrcdcne Silikatc angcwandt wcrdcn Refevcmes
p. 95.
von Bcrylliumspurcn in Silikatkann. Beryllium wird zusammen
VOL. 3 (1949)
DETERMINATION
OF
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BERYLLIUM
xnit Aluminium, van Kalzium. Magnesium, Mnngan und Eiscn mit Hilfc von Ammoniak abgcdnmit das Eiscn fliissig gchaltcn schieden, und zwar in Gegenwart von Thioglykollsiiurc, wcrden kann. Das gcfklltc Beryllium wird in L&sung gebracht und vom Titan und von Elscnspuren sowic cventucll von nndcren mitgcf&lltcn Mctallen durch Doppclschmclzung mlt Natriumhydroxyd gctrcnnt. DIG endgiiltigc Bcstimmung dcs Berylliums geschrcht auf fluorimctrischcm Wcgc untcr Anwcndung von Morin als Rcagcnsmittcl. REFERENCES 1 E. B. SANDIILL. 1mY. IZ:ng.Chewa., AtmZ. Ed., 12 (1940) 67.4. 2%. MAYR AND A. GEBAUER, Z. arlaf.Cirern.. x13 (1938) 200. 0 E. B. SANDELL, Ittd. Eng. Chctn., Atud. Ed., 12 (1940) 762.
Received April 26th, 1948