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Colorimetric and gravimetric determination of silicon in titanium and titanium alloys
VOL. 16 (1957)
ASALYTICA
COLORIMETRIC IN
Improved dctcrtnination
AND GRAVIMETRIC ‘I-I’I‘ANIUM AND
CltIhlICA
ACTA
327
DE’I‘ERMTh7ATION TITANIUM ALLOYS
mcthocls arc proposed in this paper for the colorimctric of silicon in titanium and titanium alloys.
OF SILICON ’
’
and gravimetric
Cot~l:r.r., CI.l:altiscs ,\sl.) ~oRl\‘IT%’ proposed a nc\v mctllod for the dctcnnination of silicon in titnniutn and titanium alloys hy means of the molybdenum blue color. T11c method had bccomc recognized as the only satisfactory means for determining small amounts of silicon in titanium and titanium alloys. Hotvcvcr, the method still left something to 1)~ dcsircd. Espcriciiccs in this laboratory over the past two years have shown that tllc 1>roccdurc \v,zc snhjcct to the following errors: 1. ‘I’hc fluoboric acid was found to attack tlic &a.ss\varc somewhat causing high blanks and at times erratic results. This error could bc particularly serious if the solutions wcrc filtered through the glass funnels while still tvann. It is usually assumccl that n large cscc~s of boric acid will repress the following hydrolysis: 1-I1W4 +
3H,O
.z=hH&O,
+
dH1:.
That
assumption is apparently incorrect. Tha quantity of pcmlanganatc required to oxidize the titanous ion (as much as 5 or G ml of 3’/; potassium pcmianganatc solntion, if the titanous solution has stood for only 2 or 3 hours) was found to produce at times a greenish color that caused some intcrferencc. The cffcct of tcmlxraturc on the development of the silicomolgbdate and 3. molybdenum blue colors was critical. For dctcmmining the higher ranges of silicon it wan necessary to prepare a 4. separate calibration CUT\-c. The calibration CU~-~M for both the higher and lower ranges followed 13ecr’s law, but the slopes of the two curves were considerably different. 2.
It was found that the error caused by the attack of the glassware by the fluoboric acid could be eliminated by developing the color in a plastic bottle, then diluting in Rcfermcos
9. 332
M. CODSXI~,G.
328
NOKWITZ
VOI,.
16 (1957)
I3oric acid sulution (4”/!,). hdtl So g ol boric acicl iI> illlOllt I Ho0 till of \ViltCl’ container1 in il 2 I l)yrcs bottle. Warm to al)oiit .lo”C: Lo tlissolvc. C(x>l and clilutc to 2 I. Dilute Ilvtlrofluoric iKit (3 ~I.B7). IIilirtc 150 ml of hytlrofluoric acid (5+,) to 500 ml with wntcr in n plilSl.iC bottle. Potnssium pcrmnngnmrtc soluCiun (YOA,). Store in il plastic bottle. Ammonium molyldatc solution (so/,). Tnrtnric iKid solution (zoo/i,). llctlucing solution. Dissolve 30 g of sodium bistllfitc, I g of anhydrous sodium sulfite and 0.5 g of ~-nti~ino-z-riil~~l~tliol-4-sulfoniC acid in about t 75 ml of wntcr ant1 dilute to 200 ml. Filter through n. No. 40 \VVI;atmnn~filtcr papsr ant1 store in-n plastic bottle. I’rqxLrC fresh weekly. Stnntlard silicon solution Ix ml - 0.05 mlc Sil. ‘I’hrcc nortions of sodium mctasilicatc. Na,SiO,. gFI,O, wcro wciglrcd into bchkcrs, wntcFnn2 sl;lfuric nc;tt atltlctl and the silica tlchydr&xl fn t& regular manner. I.OOOO 6 of Kn,SiO,*gl-I,0 WLS found to contain 0.097aG g of silicon (the thcorcticnl amount was 0.09873 g). 1.0303 of g the N;laSiO,,*ql-igO was tlissolvccl in water nnd dilutctl to 2 1 in a volrimctric Ilnslc. Tlic sdutitm was storccl in a was linctl Ixdtlc.
A 13cckman
;\lotlcl 1%Spcctropllotonrctcr
was usctl.
PIWcedrr YC 0.003 lo 0. I Go/:, silirorr. ‘I’rnnsfcr 0.500 g of tlic sample to n pliISt.iC bottlc, and ntltl jo ml of water ant1 5 ml of liydrofluoric acid (3 to 7) mcasl8rCr-l from iL plastic burct or carcfully with a plastic gratluntc. Let stnncl until dissiolvctl (2 0~ 3 hours, or ovcrniglit). Add 700 ml of boric acid solution (4Ok,) and 50 ml of water, atid then xlcl liyclrogcn pcroxiclc (JO’%,) until the solution I
p. 332
VOL.
16 (xg57j
DETERMINATION
OI: SILICON
329
begins to lighten in color. Four drops of hydrogen peroside will usuallv be rcquirctl if tllc solution has stood for 2 or 3 hours, 2 or 3 drops if the solution has stood overnight. ant1 none if the solution has stood for scvcral days. A slight cxccss of hydrogen pcroxidc is not harmful. Add potassium pcrmanganatc solution (3%) tlropwise until a permanent pink color is obtained, then z drops in excess. Place the plastic bottle into a r-liter beaker containing about 500 ml of boiling water. and continue the boiling for about (10 minutes. Rcmovc the Iwttlc ant1 CCJOIthe solution to 23 -& I’% in a running water bath. Add 10 ml of ammonium molybclatc solution (so/{,) mcasuretl with a pip& In IO & I minutes add 5 ml of tnrtaric acid solution (20?4,) mcnsured with a pipet. ant1 3 ml of rcclucing solution mcasurctl with n burct. The reducing solution should bc adclcd ~ to cacti individual sample immctliatcly after the addition of tlic tartaric acid. lxt stnncl 20 min. transfer to a 250 ml volumetric flask and dilute to the mark. Filter a portion of the solution through *a No. 42 \Vhatm.an filter paper, discarding the first 15 to 20 ml of solution. I’1ctcrminc the transmittance at 700 millimicrons. setting the instrument at 100 per cent transmittance with the rcagcnt blank. The reagent hlnnk is prcpnrctl by adding 5 ml of hyclrofluoric acid (3 to 7) to 40 ml of wotcr, and carrying the SiLlllplc through the dctcrrninution. ~onvcrt to lxx cent silicon by consulting the calibration curve. l’roccctl ils iLlJCJVC tlJ tllc Iwint at which the solution has lwcri hcatctl 0. r6 lo I .5’>:, silicou. in hiling water for 90 minutes. l’lacc tllc plastic l>ottlc in an ice bath ant1 cool to about ls°C. Transfer the solution to a .-_ju ml volumetric flask. immctliatcly dilute twthc mark with wntcr and pipet a ~5 ml alicluot into the original plastic hottlc. ~\cltl 4.5 ml of hytlrofluoric acid (3 to 7)# 00 ml of lmric :witl (.I’%,) nncl 7.j nil of water. and clcvolop the color ns bcforc. Convert to per cent silicon IJ~ consulting the calibration curve. I+epurcrliort of culibrufiotr cItfL’0. ‘I’mnsfcr 0.50 g samlAos of titaiiium of low silicon content to plastic bottles. hrltl 0, I, 3, 5. 7, 0. I I. i 3, ant1 15 ml portions of standard silicon solution. and carry tlic samples tl~rou~h the pwccdurc. Plot milligrams of silicon against logorithin of the transmitti~ncc.
‘I’hc gravimctric dctcrmination of silicon in titanium and titanium alloys is attcnclcd with difficulty. ZJcrchloric, hydrochloric or nitric acids cannot bc used for the dehydration, bccausc thcsc acids cause the precipitation of considerable titanium salts. Rcccntly a Task Force unclcr the chairmanship of 11. J. &TILES, Titanium Metals Corporation of America, found the sulfuric acid dehydration method for silicon in titanium and titanium alloys to be surprisingly inaccurate. An investigation was unclcrtakcn to find the causes of error in tile sulfuric acid dehydration method for silicon in titanium and titanium alloys. It was decided that no gravimetric mcthocl woulcl be satisfactory for the accurate determination of small amounts of silicon in titanium and titanium alloys. Thcreforc efforts wcrc devoted towards finding out why the sulfuric acid dehydration method gave inaccurate results over the range 0.3 to SC;/”silicon. It was found that tlic following were the chief reasons why the method was inaccumtc over that particular range: a black residue was freclucntly obtained. 1. On igniting the silica precipitates, It was deduced from the phase diagram of the titanium-silicon systcm4 that the black residue was Ti,Si,. It could not be clemcntal silicon *. ISxl~erimcntal evidence that the residue was Ti,Si, and not a higher valence silicide is in the fact that blue solutions (titanous ion) wcrc obtained when black silica precipitates were dissolved in hydrofluoric acid. Apparently Ti,$i, is quite resistant to the action of sulfuric acid. This is in contrast to the action of sulfuric acid on a solid solution of silicon in titanium (the form in which most of the silicon would be present). ‘The solid solution would be cxpcctcd to be readily attacked to produce silicic acid. CI _. The ignited silica precipitates contained occluded titanium salts of varied composition which underwent indefinite changes between the first. ignition and the ignition following the treatment with hydrofluoric and sulfuric acids. Rcfereuccs
p. 332
33’
M. CODELL,
G. NORWIT%
VOL.
16 (1957)
3. The glassy mass of titanium sulfate produced when the silica precipitates were treated with hydrofluoric and sulfuric acids and reignited were found to retain SO, with great tenacity. Obviously this can cause serious error. The fact that titanium sulfate retains SO, on ignition is in conformance with the observations of decomposing the titanium sulfate on heating may be Of YIGO’I+. The difficulty caused by the fact that the titanium sulfate present would be expected to have ‘MQxSO,~xH,O, and TiOSO, than rather Ti(SO,),a. the composition TiO,*SO,, It was found that the above errors could bc entirely eliminated by dehydrating wit11 sulfuric acid, fusing the silica with sodium carbonate and then dehydrating with perchloric acid. By this means the ‘I‘i,Si, was completely attacked and a pure white silica precipitate always obtained. After treatment with hydrofluoric and sulfuric acids and subsequent ignition practically no residue remained. Subsequent to the completion of this paper it has been brought to the authors’ attention that II. FLAER of U.S. Naval Proving Grouncls, IIahlgren, Virginia, has dcvclopcd another method for the determination of silicon in titanium and titanium alloys_ that seems to give satisfactory results. In this method the sample is brought into solution by fusing with sodium hiaulfatc in a Vycor beaker or platinum dish, and the silica then dchydratcd with sulfuric acid. ‘I’hc gravimetric mcthotl is rccommcndecl for the range 0.3 to s’i/, silicon. More than 2(x, silicon would not bc cspectcd to bc found in commercial titanium alloys since metallurgical studies 7 have shown that titanium alloys containing more than this amount of silicon have unclesirablc propcrtics.
Weigh the srrmplc into a 400 ml bcakcr. USC a z g snmplo for 0.3 to I”/, silicon and a I g sample for 1 to 5%, silicon. ~\clcl zoo ml of water ant1 .)o ml of sulfuric acid, and heat just below the hoiliny point until the sample is tlissulvccl. Add IO ml of Iiyclrogcn pcroxitlc (300A,), cvaporatc tc) fumes ol s\llfuric :tcicl :rncl fume ikt motlcratc Ilcnt for 5 to 8 min. licmovc the bcnkcr from the hot plutc irnnlccli;ttcly if the titanium sl~owu signs of Iiy~IroIysis after a few minutes fuming. Allcnv to cool, and add 300 ml of water nncl paper pulp. Irilter througl1 a No. 41 Whatman filter paper, police the bcakcr anil wash thc precipitate with zOA, sulfuric acid solution. Transfer the filter paper ant1 prccipitatc to a platinum crucible, burn off the filter paper at low heat ancl ignite for a few minutes. Fuse with sodium carbonate, ant1 tlissolvc the melt in a mixture of 250 ml of wrltcr and 40 ml of pcrchloric ncicl (70~9,) contninctl in a 400 ml beaker. Evaporate to fumes of pcrchloric acid and funic strongly for 15 min. Filter as bcforc. nntl ignite at IIoo°C for 30 min. Weigh and treat with 5 ml of hydrofluoric acid (@%,) ant1 2 drops of sulfuric acid. Evaporate to tlryncss on the hot pl;ltC, ant1 ignite at I loo% for IO min. Weigh again. The tliffcrencc in weight is siliccm tlioxidc. The f:rctor for converting silicon tlioxitlc to silicon is o.qG72.
When the original colorimctric mcthocl was developed no titanium samples of varying silicon content were available. Now several such samples are available and their silicon content is presently being clctermined by a Task Force sponsored by Watertown Arsenal. The results obtained by the authors on these samples, using the proposed methods, are shown in Table I. The results show good precision. The colorimctric and gravimetric results for sample MrA-42 are in satisfactory agreement. Sample WA-42 was the only sample that was within the range of both the colorimetric and gravimetric methocls.
16 (x957)
VOL.
DETERMINATION
-... RESULTS .--
_--_.-___
.
.
_
_.-_
_
Calorimetric
- .___. -----
_.-.--
results
-.-.-
_.
0.40
(y,{,)
TABLE PROPOSED
_---
IY/l.JI . _.-__. .__-_.
._ -_
._. - .-. _. _
UY
OF SILICOS
.___-.
331
I PROCEDURltS .. . ___...__~_ .._
,,. -.--
.._-..
__
- _._......
-
.
_ . .._ -.-
-
0..(2
0.005
0.038
0.005
o.qo
O.‘I I
0.038 0.037
-0.036 o-035, 0.03s 0.030 0.035 ” J’3.5 0.(>35
0.007 o.ooH
0..}2
Cravimctric
results
(%,)
0.41
1.91
0.4
1
I.91
O..I
.!
t .()5
0. *I ?
_.-.__...._-_.- _-.._...._ __. _ $1 National
Bureau
.._.-. __...
-
-
--
--
.-___
I.95
- .._ _..__.
of Standards
._-_.
-_.
W/I-~3
_... ._.
.
_..
._... - .
..
_
sample.
ImproVed coloritnctric an<1 grnvinictric methods arc propusccl for the tlctcrmini~tion of nilicrjn method the sample in clissolvctl in Ilyclroin titanium and titanium alloys. In the colorimctric fluoric ncid. boric acid ndtletl nntl the titanium oxidized with hydrogen pcroxiclc ilntl pcrmanganatc. The bulk of the titanium is prccipitatctl ns a crystnllinc prccipitutc hy heating in boiling Wiltl?l , ilntl the molyhdcnum color tlcvclopctl. A pJrtiOn of the solution is filtcrctl nncl the tmnsrnittancc mcasirrctl. In the gravimctric mcthocl the snniplc is funictl yitll sulfuric ucitl. the nilicn ignitctl and fuucd with sodium crrrlmnatc. ‘l’hc silica is then clchydrcltctl with Ixzrchloric ;lci
et tine mdthotlc gr;rviin&riquc sotit proposf5es pour Ic tlouagc Dans le procdtld colorimbtriquc, I’&zhantillon cat attarltrc? par l’ncidc fluorhydrique; on ajoute dc I’acidc boriquc; le titanc cat cnauitc oxyd6 par Ic pcroxydc d’hydrog&ne ct lc permanganate. 1.a majeure partie au titanc cut prdcipitCc h If&at cristallin par chauffage tlnns l’eau bouillante ct la coloration du hlcu de molyhd8nc cwt tlcvcloppCc. On filtre Unc
mCthoclc
du silicium
Une
partic
tlans
de
la
colorimdtriquc
lc titanc
et scs alliagcs.
Sohltion
Ct
On
nl~Yllrc
I’abSOrptiOn.
I)anS
k
pJCdd6
gravimbtri(lUc,
I’dChantilkJn
&vapor& avcc dc l’acide sulfurique jusqu’h formation dc fum&s blanches; la silicc form&c cst ensuite calcin& ct fondue avec du carbonate de sodium. La dice cat alors deshytlratde par l’acidc perchlarique. La methodc colorimCtriquc est recommandde pour &a tcncurs cn silicium clc 0.003 .1 X.50/1,ct la m&thodc gravim&riquc pour clcs tencurs de 0.3 B 5?;,.
cut
Eine kolorimetrischc und eine gravimetrische Methode zur Bestimmung von Silieium in Titan und Titanlegicrungen werden vorgeschlagen. Bci dcr kolorimctrischen Ucthodc wirtl die Probe in Fluorwasserstoffsiure gelbst, BorsPurc zugefiigt und das Titan mit Wasserstoffperoxyd und Permanganat oxydiert. Durch Erhitzen in kochendem Wasser f&llt man die Hauptmenge des Titans in kri&aLliner Form aus. Nun entwickelt man die Farbe dcs Molybd#nblaus. Ein Teil cler L&ung wird filtriert uncl seine Lichtdurchltisigkeit gemessen. Bei dcr gravimetrischen hlcthocle wird die Probe mit Schwefelsliure abgeraucht, das Siliziumdioxycl kalziniert und mit Natriumcarbonat geschmolzen. Das Siliziumdioxyd wird dann mit .Perchlors%uro~entwPssert. Die kolorimetrische Methode wird fLir Siliziumgehalte von 0.003 bis I ,5%, die gravimetrische f(ir Siliziumgehalte von .0.3:bis 5% empfohlen.
Kcferrncrts
p. 33a
332
M. CODELL,
VOL.
C. NORWITZ
IO
(1957)
REI;ER’ENCISS hr. CODELL, c. CLEMENCY AND G. Nonw~z, And. Chem., 25 (1953) 1432. A. 13. CARLSON AND c. V. %tNKS, Artal. Ck7Jl.. 24 (1952) 472. IC. 'JORDAN AND 13. W. L;ISCHEK, TccJr. Mill. I
Gmelins GbIUtl, C. M.
1’. 427~
System Nummcr 41, huflaga M’cinllcini/I3cr~!HtrasMc, 19.53, PP. 25% 323, 345, 375, 376. EASTWOOD, Tvuns. Am. CRAXGHEAD, 0. W. SIMMONS ANI) I,. W.
L-qys.,
J~IuIILLJJ~IcJL der A WJY~U~Iisclrcrc Clrcmie,
188
(1950)
8, \‘crlag Znsl.
Chcmic,
Mining
Met.
‘185. hCCiVCt1
UV-Sl’EC’lXA
44 (1952) 518. Hall, London,
OF
THE
COPPER CHELATE I30,XYLIC ACID
OF
OCtobCr
Igth,
1956
QUINOLINE-S-CAR-
In two previous communications it has been shown by 13nsu AND CIIA-IW~I~J~~? that a comparative study of the absorption spectra of an organic lcgand and its metal chelate can be used effectively in getting an insight into the structure of a metal chelatc. In order to give a further demonstration of the applicability of the method, we report the result of our mcasurcmcnt of the absorption spectra of the copper chelate of quinoline-8-carboxylic acid. Quinoline-8-carboxylic acid (I) is amphoteric and in solution may esist as a zwittcrion (TI). In acid solution it should exist as (III) and in alkaline solution as (IV).
In 95% ethyl alcoholic solution quinoline-8-carbosylic acid shows two absorption maxima at 295 rnp and 320 rnp respectively. In o.rM alcoholic KOH the absorption band at 320 mp disappears, while in o.rfi.1 alcoholic perchloric acid only one characteristic band appears at 3r5 rnp. This eviclently lcncls support to the zwitterion structure of quinoline-8-carboxylic acid. 1 S. UASU
AND
I<. 1;. CHATTERJEE,
NatzrrruissetrscJrclf/s,r,
42 (1955)
4x3:
43 (IgsG)
134.
ASALYTICA
COLORIMETRIC IN
Improved dctcrtnination
AND GRAVIMETRIC ‘I-I’I‘ANIUM AND
CltIhlICA
ACTA
327
DE’I‘ERMTh7ATION TITANIUM ALLOYS
mcthocls arc proposed in this paper for the colorimctric of silicon in titanium and titanium alloys.
OF SILICON ’
’
and gravimetric
Cot~l:r.r., CI.l:altiscs ,\sl.) ~oRl\‘IT%’ proposed a nc\v mctllod for the dctcnnination of silicon in titnniutn and titanium alloys hy means of the molybdenum blue color. T11c method had bccomc recognized as the only satisfactory means for determining small amounts of silicon in titanium and titanium alloys. Hotvcvcr, the method still left something to 1)~ dcsircd. Espcriciiccs in this laboratory over the past two years have shown that tllc 1>roccdurc \v,zc snhjcct to the following errors: 1. ‘I’hc fluoboric acid was found to attack tlic &a.ss\varc somewhat causing high blanks and at times erratic results. This error could bc particularly serious if the solutions wcrc filtered through the glass funnels while still tvann. It is usually assumccl that n large cscc~s of boric acid will repress the following hydrolysis: 1-I1W4 +
3H,O
.z=hH&O,
+
dH1:.
That
assumption is apparently incorrect. Tha quantity of pcmlanganatc required to oxidize the titanous ion (as much as 5 or G ml of 3’/; potassium pcmianganatc solntion, if the titanous solution has stood for only 2 or 3 hours) was found to produce at times a greenish color that caused some intcrferencc. The cffcct of tcmlxraturc on the development of the silicomolgbdate and 3. molybdenum blue colors was critical. For dctcmmining the higher ranges of silicon it wan necessary to prepare a 4. separate calibration CUT\-c. The calibration CU~-~M for both the higher and lower ranges followed 13ecr’s law, but the slopes of the two curves were considerably different. 2.
It was found that the error caused by the attack of the glassware by the fluoboric acid could be eliminated by developing the color in a plastic bottle, then diluting in Rcfermcos
9. 332
M. CODSXI~,G.
328
NOKWITZ
VOI,.
16 (1957)
I3oric acid sulution (4”/!,). hdtl So g ol boric acicl iI> illlOllt I Ho0 till of \ViltCl’ container1 in il 2 I l)yrcs bottle. Warm to al)oiit .lo”C: Lo tlissolvc. C(x>l and clilutc to 2 I. Dilute Ilvtlrofluoric iKit (3 ~I.B7). IIilirtc 150 ml of hytlrofluoric acid (5+,) to 500 ml with wntcr in n plilSl.iC bottle. Potnssium pcrmnngnmrtc soluCiun (YOA,). Store in il plastic bottle. Ammonium molyldatc solution (so/,). Tnrtnric iKid solution (zoo/i,). llctlucing solution. Dissolve 30 g of sodium bistllfitc, I g of anhydrous sodium sulfite and 0.5 g of ~-nti~ino-z-riil~~l~tliol-4-sulfoniC acid in about t 75 ml of wntcr ant1 dilute to 200 ml. Filter through n. No. 40 \VVI;atmnn~filtcr papsr ant1 store in-n plastic bottle. I’rqxLrC fresh weekly. Stnntlard silicon solution Ix ml - 0.05 mlc Sil. ‘I’hrcc nortions of sodium mctasilicatc. Na,SiO,. gFI,O, wcro wciglrcd into bchkcrs, wntcFnn2 sl;lfuric nc;tt atltlctl and the silica tlchydr&xl fn t& regular manner. I.OOOO 6 of Kn,SiO,*gl-I,0 WLS found to contain 0.097aG g of silicon (the thcorcticnl amount was 0.09873 g). 1.0303 of g the N;laSiO,,*ql-igO was tlissolvccl in water nnd dilutctl to 2 1 in a volrimctric Ilnslc. Tlic sdutitm was storccl in a was linctl Ixdtlc.
A 13cckman
;\lotlcl 1%Spcctropllotonrctcr
was usctl.
PIWcedrr YC 0.003 lo 0. I Go/:, silirorr. ‘I’rnnsfcr 0.500 g of tlic sample to n pliISt.iC bottlc, and ntltl jo ml of water ant1 5 ml of liydrofluoric acid (3 to 7) mcasl8rCr-l from iL plastic burct or carcfully with a plastic gratluntc. Let stnncl until dissiolvctl (2 0~ 3 hours, or ovcrniglit). Add 700 ml of boric acid solution (4Ok,) and 50 ml of water, atid then xlcl liyclrogcn pcroxiclc (JO’%,) until the solution I
p. 332
VOL.
16 (xg57j
DETERMINATION
OI: SILICON
329
begins to lighten in color. Four drops of hydrogen peroside will usuallv be rcquirctl if tllc solution has stood for 2 or 3 hours, 2 or 3 drops if the solution has stood overnight. ant1 none if the solution has stood for scvcral days. A slight cxccss of hydrogen pcroxidc is not harmful. Add potassium pcrmanganatc solution (3%) tlropwise until a permanent pink color is obtained, then z drops in excess. Place the plastic bottle into a r-liter beaker containing about 500 ml of boiling water. and continue the boiling for about (10 minutes. Rcmovc the Iwttlc ant1 CCJOIthe solution to 23 -& I’% in a running water bath. Add 10 ml of ammonium molybclatc solution (so/{,) mcasuretl with a pip& In IO & I minutes add 5 ml of tnrtaric acid solution (20?4,) mcnsured with a pipet. ant1 3 ml of rcclucing solution mcasurctl with n burct. The reducing solution should bc adclcd ~ to cacti individual sample immctliatcly after the addition of tlic tartaric acid. lxt stnncl 20 min. transfer to a 250 ml volumetric flask and dilute to the mark. Filter a portion of the solution through *a No. 42 \Vhatm.an filter paper, discarding the first 15 to 20 ml of solution. I’1ctcrminc the transmittance at 700 millimicrons. setting the instrument at 100 per cent transmittance with the rcagcnt blank. The reagent hlnnk is prcpnrctl by adding 5 ml of hyclrofluoric acid (3 to 7) to 40 ml of wotcr, and carrying the SiLlllplc through the dctcrrninution. ~onvcrt to lxx cent silicon by consulting the calibration curve. l’roccctl ils iLlJCJVC tlJ tllc Iwint at which the solution has lwcri hcatctl 0. r6 lo I .5’>:, silicou. in hiling water for 90 minutes. l’lacc tllc plastic l>ottlc in an ice bath ant1 cool to about ls°C. Transfer the solution to a .-_ju ml volumetric flask. immctliatcly dilute twthc mark with wntcr and pipet a ~5 ml alicluot into the original plastic hottlc. ~\cltl 4.5 ml of hytlrofluoric acid (3 to 7)# 00 ml of lmric :witl (.I’%,) nncl 7.j nil of water. and clcvolop the color ns bcforc. Convert to per cent silicon IJ~ consulting the calibration curve. I+epurcrliort of culibrufiotr cItfL’0. ‘I’mnsfcr 0.50 g samlAos of titaiiium of low silicon content to plastic bottles. hrltl 0, I, 3, 5. 7, 0. I I. i 3, ant1 15 ml portions of standard silicon solution. and carry tlic samples tl~rou~h the pwccdurc. Plot milligrams of silicon against logorithin of the transmitti~ncc.
‘I’hc gravimctric dctcrmination of silicon in titanium and titanium alloys is attcnclcd with difficulty. ZJcrchloric, hydrochloric or nitric acids cannot bc used for the dehydration, bccausc thcsc acids cause the precipitation of considerable titanium salts. Rcccntly a Task Force unclcr the chairmanship of 11. J. &TILES, Titanium Metals Corporation of America, found the sulfuric acid dehydration method for silicon in titanium and titanium alloys to be surprisingly inaccurate. An investigation was unclcrtakcn to find the causes of error in tile sulfuric acid dehydration method for silicon in titanium and titanium alloys. It was decided that no gravimetric mcthocl woulcl be satisfactory for the accurate determination of small amounts of silicon in titanium and titanium alloys. Thcreforc efforts wcrc devoted towards finding out why the sulfuric acid dehydration method gave inaccurate results over the range 0.3 to SC;/”silicon. It was found that tlic following were the chief reasons why the method was inaccumtc over that particular range: a black residue was freclucntly obtained. 1. On igniting the silica precipitates, It was deduced from the phase diagram of the titanium-silicon systcm4 that the black residue was Ti,Si,. It could not be clemcntal silicon *. ISxl~erimcntal evidence that the residue was Ti,Si, and not a higher valence silicide is in the fact that blue solutions (titanous ion) wcrc obtained when black silica precipitates were dissolved in hydrofluoric acid. Apparently Ti,$i, is quite resistant to the action of sulfuric acid. This is in contrast to the action of sulfuric acid on a solid solution of silicon in titanium (the form in which most of the silicon would be present). ‘The solid solution would be cxpcctcd to be readily attacked to produce silicic acid. CI _. The ignited silica precipitates contained occluded titanium salts of varied composition which underwent indefinite changes between the first. ignition and the ignition following the treatment with hydrofluoric and sulfuric acids. Rcfereuccs
p. 332
33’
M. CODELL,
G. NORWIT%
VOL.
16 (1957)
3. The glassy mass of titanium sulfate produced when the silica precipitates were treated with hydrofluoric and sulfuric acids and reignited were found to retain SO, with great tenacity. Obviously this can cause serious error. The fact that titanium sulfate retains SO, on ignition is in conformance with the observations of decomposing the titanium sulfate on heating may be Of YIGO’I+. The difficulty caused by the fact that the titanium sulfate present would be expected to have ‘MQxSO,~xH,O, and TiOSO, than rather Ti(SO,),a. the composition TiO,*SO,, It was found that the above errors could bc entirely eliminated by dehydrating wit11 sulfuric acid, fusing the silica with sodium carbonate and then dehydrating with perchloric acid. By this means the ‘I‘i,Si, was completely attacked and a pure white silica precipitate always obtained. After treatment with hydrofluoric and sulfuric acids and subsequent ignition practically no residue remained. Subsequent to the completion of this paper it has been brought to the authors’ attention that II. FLAER of U.S. Naval Proving Grouncls, IIahlgren, Virginia, has dcvclopcd another method for the determination of silicon in titanium and titanium alloys_ that seems to give satisfactory results. In this method the sample is brought into solution by fusing with sodium hiaulfatc in a Vycor beaker or platinum dish, and the silica then dchydratcd with sulfuric acid. ‘I’hc gravimetric mcthotl is rccommcndecl for the range 0.3 to s’i/, silicon. More than 2(x, silicon would not bc cspectcd to bc found in commercial titanium alloys since metallurgical studies 7 have shown that titanium alloys containing more than this amount of silicon have unclesirablc propcrtics.
Weigh the srrmplc into a 400 ml bcakcr. USC a z g snmplo for 0.3 to I”/, silicon and a I g sample for 1 to 5%, silicon. ~\clcl zoo ml of water ant1 .)o ml of sulfuric acid, and heat just below the hoiliny point until the sample is tlissulvccl. Add IO ml of Iiyclrogcn pcroxitlc (300A,), cvaporatc tc) fumes ol s\llfuric :tcicl :rncl fume ikt motlcratc Ilcnt for 5 to 8 min. licmovc the bcnkcr from the hot plutc irnnlccli;ttcly if the titanium sl~owu signs of Iiy~IroIysis after a few minutes fuming. Allcnv to cool, and add 300 ml of water nncl paper pulp. Irilter througl1 a No. 41 Whatman filter paper, police the bcakcr anil wash thc precipitate with zOA, sulfuric acid solution. Transfer the filter paper ant1 prccipitatc to a platinum crucible, burn off the filter paper at low heat ancl ignite for a few minutes. Fuse with sodium carbonate, ant1 tlissolvc the melt in a mixture of 250 ml of wrltcr and 40 ml of pcrchloric ncicl (70~9,) contninctl in a 400 ml beaker. Evaporate to fumes of pcrchloric acid and funic strongly for 15 min. Filter as bcforc. nntl ignite at IIoo°C for 30 min. Weigh and treat with 5 ml of hydrofluoric acid (@%,) ant1 2 drops of sulfuric acid. Evaporate to tlryncss on the hot pl;ltC, ant1 ignite at I loo% for IO min. Weigh again. The tliffcrencc in weight is siliccm tlioxidc. The f:rctor for converting silicon tlioxitlc to silicon is o.qG72.
When the original colorimctric mcthocl was developed no titanium samples of varying silicon content were available. Now several such samples are available and their silicon content is presently being clctermined by a Task Force sponsored by Watertown Arsenal. The results obtained by the authors on these samples, using the proposed methods, are shown in Table I. The results show good precision. The colorimctric and gravimetric results for sample MrA-42 are in satisfactory agreement. Sample WA-42 was the only sample that was within the range of both the colorimetric and gravimetric methocls.
16 (x957)
VOL.
DETERMINATION
-... RESULTS .--
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.
.
_
_.-_
_
Calorimetric
- .___. -----
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results
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0.40
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OF SILICOS
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0.007 o.ooH
0..}2
Cravimctric
results
(%,)
0.41
1.91
0.4
1
I.91
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sample.
ImproVed coloritnctric an<1 grnvinictric methods arc propusccl for the tlctcrmini~tion of nilicrjn method the sample in clissolvctl in Ilyclroin titanium and titanium alloys. In the colorimctric fluoric ncid. boric acid ndtletl nntl the titanium oxidized with hydrogen pcroxiclc ilntl pcrmanganatc. The bulk of the titanium is prccipitatctl ns a crystnllinc prccipitutc hy heating in boiling Wiltl?l , ilntl the molyhdcnum color tlcvclopctl. A pJrtiOn of the solution is filtcrctl nncl the tmnsrnittancc mcasirrctl. In the gravimctric mcthocl the snniplc is funictl yitll sulfuric ucitl. the nilicn ignitctl and fuucd with sodium crrrlmnatc. ‘l’hc silica is then clchydrcltctl with Ixzrchloric ;lci
et tine mdthotlc gr;rviin&riquc sotit proposf5es pour Ic tlouagc Dans le procdtld colorimbtriquc, I’&zhantillon cat attarltrc? par l’ncidc fluorhydrique; on ajoute dc I’acidc boriquc; le titanc cat cnauitc oxyd6 par Ic pcroxydc d’hydrog&ne ct lc permanganate. 1.a majeure partie au titanc cut prdcipitCc h If&at cristallin par chauffage tlnns l’eau bouillante ct la coloration du hlcu de molyhd8nc cwt tlcvcloppCc. On filtre Unc
mCthoclc
du silicium
Une
partic
tlans
de
la
colorimdtriquc
lc titanc
et scs alliagcs.
Sohltion
Ct
On
nl~Yllrc
I’abSOrptiOn.
I)anS
k
pJCdd6
gravimbtri(lUc,
I’dChantilkJn
&vapor& avcc dc l’acide sulfurique jusqu’h formation dc fum&s blanches; la silicc form&c cst ensuite calcin& ct fondue avec du carbonate de sodium. La dice cat alors deshytlratde par l’acidc perchlarique. La methodc colorimCtriquc est recommandde pour &a tcncurs cn silicium clc 0.003 .1 X.50/1,ct la m&thodc gravim&riquc pour clcs tencurs de 0.3 B 5?;,.
cut
Eine kolorimetrischc und eine gravimetrische Methode zur Bestimmung von Silieium in Titan und Titanlegicrungen werden vorgeschlagen. Bci dcr kolorimctrischen Ucthodc wirtl die Probe in Fluorwasserstoffsiure gelbst, BorsPurc zugefiigt und das Titan mit Wasserstoffperoxyd und Permanganat oxydiert. Durch Erhitzen in kochendem Wasser f&llt man die Hauptmenge des Titans in kri&aLliner Form aus. Nun entwickelt man die Farbe dcs Molybd#nblaus. Ein Teil cler L&ung wird filtriert uncl seine Lichtdurchltisigkeit gemessen. Bei dcr gravimetrischen hlcthocle wird die Probe mit Schwefelsliure abgeraucht, das Siliziumdioxycl kalziniert und mit Natriumcarbonat geschmolzen. Das Siliziumdioxyd wird dann mit .Perchlors%uro~entwPssert. Die kolorimetrische Methode wird fLir Siliziumgehalte von 0.003 bis I ,5%, die gravimetrische f(ir Siliziumgehalte von .0.3:bis 5% empfohlen.
Kcferrncrts
p. 33a
332
M. CODELL,
VOL.
C. NORWITZ
IO
(1957)
REI;ER’ENCISS hr. CODELL, c. CLEMENCY AND G. Nonw~z, And. Chem., 25 (1953) 1432. A. 13. CARLSON AND c. V. %tNKS, Artal. Ck7Jl.. 24 (1952) 472. IC. 'JORDAN AND 13. W. L;ISCHEK, TccJr. Mill. I
Gmelins GbIUtl, C. M.
1’. 427~
System Nummcr 41, huflaga M’cinllcini/I3cr~!HtrasMc, 19.53, PP. 25% 323, 345, 375, 376. EASTWOOD, Tvuns. Am. CRAXGHEAD, 0. W. SIMMONS ANI) I,. W.
L-qys.,
J~IuIILLJJ~IcJL der A WJY~U~Iisclrcrc Clrcmie,
188
(1950)
8, \‘crlag Znsl.
Chcmic,
Mining
Met.
‘185. hCCiVCt1
UV-Sl’EC’lXA
44 (1952) 518. Hall, London,
OF
THE
COPPER CHELATE I30,XYLIC ACID
OF
OCtobCr
Igth,
1956
QUINOLINE-S-CAR-
In two previous communications it has been shown by 13nsu AND CIIA-IW~I~J~~? that a comparative study of the absorption spectra of an organic lcgand and its metal chelate can be used effectively in getting an insight into the structure of a metal chelatc. In order to give a further demonstration of the applicability of the method, we report the result of our mcasurcmcnt of the absorption spectra of the copper chelate of quinoline-8-carboxylic acid. Quinoline-8-carboxylic acid (I) is amphoteric and in solution may esist as a zwittcrion (TI). In acid solution it should exist as (III) and in alkaline solution as (IV).
In 95% ethyl alcoholic solution quinoline-8-carbosylic acid shows two absorption maxima at 295 rnp and 320 rnp respectively. In o.rM alcoholic KOH the absorption band at 320 mp disappears, while in o.rfi.1 alcoholic perchloric acid only one characteristic band appears at 3r5 rnp. This eviclently lcncls support to the zwitterion structure of quinoline-8-carboxylic acid. 1 S. UASU
AND
I<. 1;. CHATTERJEE,
NatzrrruissetrscJrclf/s,r,
42 (1955)
4x3:
43 (IgsG)
134.