The micro volumetric determination of uranium with application to bismuth base alloy analysis

ASALSTICA

220

THE

CHIMICA

ACTA

\‘OI. 17 (r9571

,MICRO VOLUMETRIC DETERMINATION OF URANIUM APPLICATION TO IUISMUTH BASIS ALLOY ANALYSIS

WITH

INTRODUC 1 ION

The volurnctrrc dctcrmlnatron of uramum on a macro ant1 semi micro scale by reduction to the tetravalent state with a lead rcductor followed by titration against ccric sulphatc IS now a well cstabllshcd proccdur+*. ‘I’hc need arose for a method for the determmation of small amounts of uramum m bismuth base alloys. These alloys wcrc expected to contam small amounts of alrconlurn, calcium and iron m addition to from o.005 to o TO/’ of uranium. The dctermlnatlon of such small amounts of uranium rccluircd clthcr an cxtcnslon of the volumetric method to the microgram lcvcl of uranium or, alternatlvcly, the apphcation of absorptlomctric or polarographlc procedures. Various consldcratlons including that of adcquatc %ensitlvlty at the lowest conccntratlons of uranium favourcd the volumetrrc method with the consequent dcvclopment of the micro lead rcductor dcscribcd m this paper. Unfortunately, this rcductor method coulcl not bc: applied dlrcctly m the presence of bismuth and iron, and scparatlon procedures proved necessary for the determmatlon of uramum in bismuth base alloys.

A ~~lctl tlown vcls1011 of die inncro rctlilctor way found ~uit~blc for the tlctcrnilnatlon of sniull ,inioiintu ul 1lriLIllurn It wa5 rnrrtlc from .i 10 ctn lcnyth uf glds9 tubing of 3 xii111 lntcrnd dlamctcr .ttltl wltlr .Lcnpxlty of dbotit 0 3 nil. ‘I’0 ib)ri\t tllc triltlsfcr of sduttons to tllo rcductor, it small flltcr funnel of iLl)Ullt 3 ml capacity Wd:, flXct1 to tllc top Of tlIc LlllIC by R p0lytlIcIlc Ylccvc A snl,Lll glass Ilnll of ~\lI~~rO\lIlli~tcly 2 lI1Ilk in tlI.~Illctcl siipportctl tlrc colilnin of granuI.rtctl Ic.id (.10&o nrcsh) wli~cli ,rltnost fdlcd the rctluctor I’lrc flow of 11qu1tl from the lower tip could bc 4tqqxxl when ncccs.q.lry by piislllng on .L piccc of lIlliLll bore soft rubber tube !+lllti\bly clowtl nt tlIc lower end 11 plug cd this type proved nccc4unry to prcvcnt air bcliig forcctl into tlic rctluctor III tlic process of stappng tllc fl,OW of llqulcl L‘llIl tlCtilll\ Of tllc rctluctor ilrc yivan 111 1:Ig. I ‘Tlrc rctluctor was prcp,~rccI from good grdo granubtccl Ic.rtl (~0-00 mesh) kept untlcr loO,:, v/v Irytlloclrlor~r. ncd Sufflctcnl of tlrl* mutcrd wa?r t.lkcn and stlrrctl to break clown any aggrcgntcs of tlw hitI pai ticks At tlrc cli\IllL’ tllnc the rctluctor column ant1 funnel was flllcd wltli lo:{, v/v IiytIrod~lor~c ncitl .~:irl cx.lmlnctl to CIIYIIIO tlic conlplctc dbscncc of nlr biibblcs ‘I’lrc lend was next tmnafci rctl to tlrc column wit11 tlic at1 of n strcnm of lo?<, 8 /v Irytlrochlur~c ncid from a wash bottle, whdst .~llowi~ig hOInc of tlic iicccl to run out of tlic roductor WIG lcad wns ull0wctl to nygrcgatc by gently tappIng the colunrn curt1then the actd \vi\\tlrnlncd down to tlrc top of the funnel stern I I the lend chd not p csenL d bright mctdhc siirfixc, iL was ncccvsnry to trcnt tliu column wltli conccntrntcd by plnclng the end of the rctluctor IIIu.bcnkcr of conccntratcd lryclrochlorlc ac~tl ‘Tlus cm be ucll~cvctl Rcfe~occcs

fi

2a5

VOL.

17 (1957)

MICRO

VOLUMETRIC

DETERMISA~ION

OF

URASIUM

hydrochloric aced and then applying suction to the other cncl to suck the nad up through the column I3y adclrng toy,, v/v hyclroclrlorlc actrl to the bcakcr ancl conttnulng the suction proccdurc, the weaker aced can bc rc-lntrotluccd Into the reductor column without the lntrotluctlon of air It IS important to m.untam the lcvcl of acid almvc the lcatl in the funnel stem and for efflocnt working It IS gcncrnllv nccesrnry to rcpnck the column each day Uranrum i?rrcduccd by the pa~~agc of ;L qtolutlon of tlic matcrlJl In L ml or lesv of to:;, v/v hytlrochloric ncltl through the rcductor, fo~~owctl try I ml of this acid to wnvh the rcductor This solution 15 collcctcd in a 5 ml tall-form macro bcnkcr The urdniuni IS then titrated Hltll stantl.lrd CWIC sulphntc which IS added from an hgla hyrmgc hurcttc hrcttc IS fitted with a rnicromctcr screw. ‘I’llC t1p of the statwnnry ant1 lmmcrsctl bcncath the Itquid In the bcakcr. l’hc lwokcr on the other ham1 IS sccurctl by ndhcstvc to a horizontal plntfortn which can IX rot;itctl by an air-driven stlrrcr and by this means thorough mixing of the solution IS obtained during the titrntlon procctlurc ‘I ho solution iY mada npproxlmzttcly normal in sulpliurlc .Lcid before the uranium is titrated ngain4t ccric sulphntc crthcr thrcctlp in the prcscncc of o oz ml of phosphoric .~c~tl (‘1’ gr I 75) using fcrroin 0s the intliciltor or intlircctly ,Lftcr tlic ~~tltl~tion of fcrrlc Aurn. the ferrous tron protlucctl LKIIIK tltr;rtccl III this case .lgaln with fcrroln A\ the Indlcntor ‘I’hc ferrous iron III the fcrroin ;&o consiinicb ccric sulpliiltc ant1 tlicrcforc tlic amount of Intlic.ltor usctl must LX carefully nicasiirctl I’hc lndlcntor blank constltutcs the major p.trt of the tltratccm blank. since the bl,rnk on the column I* \m;111and tcntls to disappear with 11s~ of ttlc culumn flc 0 0~ ml of 0 0orN fcrrotn rccomrncntlctl fur most tltmtlons protluccs .I IAtnk tltrc of 0 8 ccl of 0 05,X’ ccric sulph,itc which 14 cquivalciit to 4 8 pg of iirnniuni

221

Fmltcr

funnol

Llquld

level

Led

ICVCI

Leod

CIOSS

nn

FLOW

ball

CONTROL

Rubber

PLUC3

tube

it-

wGclo66

1’1~

I

I’llc

micro

rod

Ic.~l rccluclor

Ttic complctc proccdurc for tlic dctcrmin,~tloii of niiciqram aliquots of J stantlnrd sdution of urnnium In Io7& v/v hytlroctiloric

nnrounta was tcstctl on *ultablc ac~tl This solution w.u3 prcpnrctl from pUrC U,o, by trcatlng It With asnlil~l .?nl(JllntOf pCrChhrlC .ICld :\nd hciItlng toeffect the 5ollltlOn .~id so ns to contain I Iiig of of ttic oxltk ‘I’liis solution wi14 dilutccl with loC’;, v/v hytlrocllloric urclnlunr per ml of solution. that 1s I pg per nrlLrol ltrc Siiitablu a?liquots wcrc tlispcnwtl from Rscconcl Agla mlCrot)urcttc and pz~sscd down tlrc micro rcductor after mix!ng with z ml or less of too//ov/v Irydrodiloric ,icitl \‘ariou3 amounts of uranium in the range from r-500 pg wcrc tlctcrnuncd by the complctc mcthotl usrng both the rltroct and the lntllrcct tltratlon procctlurcs ‘1 hc results arc given in Table I from which it can IX qccn that goocl rccovcrics wcrc obtoinctl at ;,I1 lcvcls The titrations wcrc cnrrlcd out with tllffcrcnt Ytrcngths of ccrlc \ulphntc In the rrrngc from o 01 to o a5rV and with amounts of fcrroin inclicntor varying from 0 02 nil of 0 00ozgN to 0 0-t m) of 0 001 N, Jcpcnthng on l’lic accuracy of the rlctcrinination wa9 studlctl in sonic tlctclll ilt the amount of uranium prcscnt th! 7pg kVCl Of Uranium ~VCrd dCt~rmln~tlon~ WCrc Carrlcd (Jut tay dlfkwnt OlxratOrs uslngo o 1N ccric sulphntc and 0 02 ml of 0 00 IN fcrroin Under thcnc conditlon~ tlic cocfficicnt of variation wn* cCrlc sulphatc ;r*~cl0 04 ml of I”,:, ;rnd tlic urimlum rccovcry was low by I’;‘:, x-h2 U’(C 0r 0 05,V 0 001 N Icrrom is rccommcntlccl in tlrc titrntlon procctlurc a9 being siiltablc for most bi T!)?\cY

TYPICAL I

Dttecl

Urantum

RESULTS

falralron tnkcn.

proccd~cte

HHCOVLHY

OY

UWASIUM

IIY

10

Go

119

LO 0

Gz

Il.8

10 9

Irlrolrora procedure taken, Pg

50 0

100

250

500

rccovercd,

50 0

101

249

rccovcrctl,

a. Indttecl

References

‘I-Hi<

09

Uranium Uranrum Uranium

YOU

Q aa

clg

148

pg

-

$98

l-HI?

5lICXO

50 o 50 o

LEAD

100 101

111

DULTOH

250 247

500 497

222

G. W. C. MILNER,

G.

A. BARNETT

VOL.

17 (1957)

The belraviotrrof other elements an fireuranaum determinalaon The bchaviour of other elements was not exammcd very thoroughly in .this mvestigatlon, because mformation 1s available for many elements from the studies with the macro lead reductor and those substances causing mtcrference with the macro rcductor could be expected to cause difficulty on the micro scale. In this work, therefore, the bchaviour of only those clemcnts prcscnt m the alloy samples was checked. Bismuth caused scrtous difficulties bccausc it is reduced to the metal forrnmg a deposit at the top of the rcductor and thereby gradually blocks the column. In the case of zirconium. although it caused no difficulty in the reduction process, troubles were encountered in the direct titration due to the precipitation of zirconium phosphate. The mcltrect titration still applied, however, and the colour change from brown to green at the end-point was readily dctccted. Under these conditions a ten fold cxccss of zircomum did not interfere in the uramum determination. In the cast of thorium there was no difficulty in the direct titration procedure even for a hundred fold excess of this clement. However, on the basis of information from the macro rcductor method for uranium, mtcrfercnccs to be avoided arc chtefly iron, nitrate (and mtrttc) and organic matter. -

Y

The determination of ftre rrrantum content of bismuth base alloys A procedure was requrrccl for the dctcrmmation of the uramum content of bismuth base alloys contaming from 50 to rooo p.p.m. of uramum, 2oo-300 p.p.m. of both calcmm and zirconium and small amounts of contammatmg iron. In view of the unfavourablc bchaviour of bismuth with the lead reductor, the prchmmary removal of the bismuth from the uranium was absolutely essential. The separation of iron from uranium was also necessary bcforc the lead rcductor method for uramum could be applied. This latter separation can bc readily effected by an anion exchange procedure reported by ARNPELT 3. In this method a sulphate solution of the sample is adjusted to PH z and the iron is then reduced to the ferrous state. On passmg this solution through a small column of Dcacidttc FF in the sulphatc form, the uranium is retained on the column whereas many other clcmcnt R includmg iron are not rctaincd. The uranium can then bc subscqucntly rccovcred from the column m dilute hydrochloric acid (~0% v/v) and its concentration determined volumetrically after the destructton of orgamc matter present in solution from the ion-exchange column. Unfortunately, this separation proccdurc cannot be apphcd simultaneously to the removal of bismuth, smcc bismuth is not in solution at pry 2 and would cause blockage of the ion exchange column. Several methods are available for the separation of bismuth from uranium and consideration was given to most of them. An ion cxchangc process mvolvmg the passage of a solution of the sample m N hydrochloric acid through a column of Deacidite FF m the chloride form is one possible proccdurcd. However, tt was finally concluded that a method involving two ion-exchange scparattons would bc too time consuming fat routine analysis. A possible single ion exchange process to effect the separation of the bismuth and iron on one column was next cxammcd. This consisted of passing the sample solution in 4N hydrochloric acrd down a column of Deacidlte FF in the chloride form after the addition of stannous chloride to the solutron to reduce iron to the ferrous state. Under these condrtions the uramum is retamed on the column Rs~ere~~ccs p aa

VOL.

17 (1957)

MICRO VOLUMETRIC

DETERMIXATION

OF

UHASlUhf

223

with bismuth and tm, whereas the reduced Iron passes through. The uranium can then be recover&d by the passage of dllutc hydrochlonc acid through the column and the detcrmmation completed volumetrically. This procedure proved unsatisfactory m practice, however, because of difficulty m avoiding pick up of iron inherent in the large resin columns when carrying out the hydrochlonc acid procedure According to UURSTALL ASD M’ELLS~ the separation of uranium from bismuth and Iron is posslblc by cellulose column chromatography, bismuth and iron bcmg retained on the column whilst the uranium passes through m the ether-nitric acid cluant. Experiments soon showed however that although this technlclue was satisfactory with amounts of blsmuth of about roe mg, it was not suitable for larger samples. Another method for the separation of bismuth IS based on the fairly low bollmg point of bismuth bromide. On cvaporatmg a bismuth solution down to dryness in the prcsencc of a mixture of bromine and hydrobromlc acid, the bismuth can be volatlhsed from the beaker It IS generally necessary to heat the walls of the beaker with a bunsen flame to remove any condensed bismuth from them. On repeating this evaporation process with several separate portions of the bromine-hydrobromlc acid mixture, it is possible to remove quite readily amounts of bismuth up to rooo mg. This separation method was applied to this problem and it fitted m well wrth the subsequent ron-cxchangc process for the separation of uramum from iron. The final residue from the evaporation procedure was simply dissolved m 2-3 drops of concentrated sulphurlc acid and this solution lvas diluted to a volume of 25 ml. After the adjustment of the pt~ to a value of 2, the iron was rcduccd to the ferrous state with sulphur dioxide and the ion-exchange separation of the uranium then carried out. Full details of the complete procedure for the analysis of alloy samples are as follows:

Wc~gh out I g of the alloy, tl~ssolve m soy;, v/v mtrlc nc~tlIn a IOO ml bcakcr and then cvaporntc to dryness Add about 2 ml of J bromtnc solution contaimng Ry,::, v/v of hyclrobromlc acid. IS’!<, v/v of hromlnc and o : g of potassium bromldc per loo ml Place the benkcr In an cfflclcnt fume hood and cvnporatc to tlrvncss Gcntl) flnmc the bcakcr wlth a bunscn and cuntlnuc hcatmg to tlrl\c off the btsmuth \Vhcn the cvnporatlon ccasus, cool the bcakcr and add a further r-3 ml portlon of tlrc tromlnc mlxturc Agam cvnporato to dryness on a hot plntc and repeat the fuming procedure Repent the process four or flvc times to cnsurc tht* removal of the bismuth Cool the hcaker after the last cvnporatlon, add 2-3 drops of conccntrntcd sulphurlc aLld to d~solvc the reslduc and dllutc the soliitlon with water to a volume of about rg ml AdJust the PH of ttrlr solution to a value of 2 by the oclcl~tton of ammomum lrydroxtd; Then ndd a few crystals of o-phenantl~roltne and 2 ml’of a saturated solution of sulphur d~oxldc rn water Warm the solution on a hot plate to effect the reduction of the Iron, the tntcnslty of the colour of the solution bccomlng constant when the rcductlon renchcs complctmn Cool and rexrvc for the ton-c-clrangc wparatlon Make a 2 ml column of Dcacltlltc I:F rcsln of JO-60 mesh (see FIR z) Prepare the rc41n by grlndlng sonic of the commercial rcsln (- 16 + 50 mcqh) tn the chlorltlc form nntl sieving the matcrral to obtain that which ~35~s through n 40 tncsh JLCVC Wash the rcsln In a large column with dllutc sulphurtc nc~d untrl tlrc cfflucnt contains a ncghglblc qunntlty of chlorldc Prepnrc a smnllcr column from this mntcrlal and pnss the sample solution down It at the rate of I drop cvcry 5 qcconds 1 hen wabh the column with ;L few ml of very ddutc sulphurlc acid n
G. W. C. MILSEI<,

224

G. A. BARSETT

with a standard o OS.\’ ccr~csuI~~l~atc solution imd calculntc the results from the fact that I pl of o ogN CWIL sulphatc Carry out a blank I\ cqulvalcnt to 5 05 pg of clrnnlurn hl*o, illways dztcrrnlnatmn on the complctc procctlurc test the hxtl rcductor w~tti known ilmounts of uranium I&fore rcduclng any snmplc soliltcons A satlsfnctory urilnlum stimtlnrtl solution 1s matlc by clln*olvIny I 179 g of U,O. In nn Inltcal LO ml of pcrchlorlc ncd wlth hcatlng , ‘1 hlu solution IS tlllutcd to J I 1Jwng IO’%, I-ICI I pl = I pg U IasUL’l

S

AND

VOL.

17 (1957)

FlItor funnd

\i

Hi-

Llqdd IOVUI

CONCLUSIONS

The complete proccdurc has been tested on synthetic alloy samples prepared from bismuth metal of bcttcr than 99.9g”/” purity. The other constituents were of Specpurc or AnalaR quahty and roe p.p.m of iron was included in each sample. Thcsatlsfactory results for uranium by this proccdurc arc given in Table II. These results take into account blank dctcrmlnatlons carried out on synthetic samples contammg no uranrum. ‘The full blank gcncrdly amounted to a uranium equivalent of about rg pg, approximately one quarter of this, howcvcr, arising from the mdlcator blank alone.

~Ococldite

z

I

-GIos8

FF

boll

the resm

to upport

column

Small anIon-cxchnnye column

‘I hc mnLr0 volumctrlc nicthutl for the tlctcrmlnntlon of uramurn by tltrntion against stnndnrd ccrlc sulph.\tc nftcr lcduction on 3 Lead column has been nuccc~dully npplxd on the micro Ycd0 MIcrogram trmount?r of uramum can bc dctormlncd by this nrcthucl, tlrc lowest amount dctcrmlnablc bang ubout I mlcrogmtn TIN proccclurc IS accurntc to within f I%, at the 100pg level of uribnlum Although bismuth ant1 iron cnusc difficulty, there JY no Jntcrfcrcncc from /Irconium or thorium ‘IhIs nactlrotl for uranium ha been rrpphcd to the onnlysls of bJsmutlr bnsc dloys contcllnmg urantum in conccntmt~ons from 0 005 to 0 I$& by wciglit

1.n mcthodc volumdtr~quc pour lc closagc tic I’urnnlum. pnr tJtrrrgc nu moycn d’unc solution &don tic sulfntc dc cbrliim .tprtin r&luction sur unc colonnc de plomb, ,I dtc! npphqudo avcc succhs B dcs dosages mlcrocllrmiq\~cs IX33 traces d’uranlum pcuvcnt Otrc dovdev par cettc mdllrodc, 10 plus pctlto

qunntitd titrnblc &ant d’cnvlron I pg Cc dosage cst prCciv f I’%, pour 100 pg d’urnmum Le Ixsmuth ct Ic fcr gbncnt. cc qul n’cst pas lo cas du zn-comum ou du thorium Cottc mdthoclo D pu Gtrc appl~quch h l’andyso dcu nlhngcs B bnsc du bismuth rcnfcrmnnt o 005 h o.lO/u d’urclmum Rc/ewnccc

p

225

VOL.

17 (1957)

.MICRO VOLUMETRIC

DETERMISATION

OF URANIUM

225

Ilic makrovolumctrlschc Mcthode zur Beut~mmung von Uran tlurclr Tltrlcrcn mit cmer Standard< crsutfat-LOsung nach Rctluktton auf clncr Dl~~shulc wurdc mJt Erfotg fur M tikromcngcn angcwcnttct Mlkrogramm-Mcngcn an Uran kt)nncn mlt H~lfc theser hietlrodc bcstlmmt wcrtlcn. wobc~ due 1st gcnau inncrhalb nlctlrlgste bcstlmmbarc Xlcngc ungcfahr I Mlkrogramm 1st IIns Vcrhhrcn & I(‘;, 1x1 Gchaltcn von tlcr Grdsscnortlnung IOO eg Urnn Obwoht \Vismuth untl EIscn Scl~wcr~gkcrtcn Ixrcitcn. stOren Zlrkonlum und Thorium nlcht L~ICSC Mcthodc wurdc 7ur AnaIysc van I.cglcrungcn auf \VIsmuthbiwls, wclchc Uran In Konzcntrattoncn van o 005 l~so I Gewtchtsprotcnt cnthaltcn. nngcwcndct IIEFERESCES

I~cccivccl Janu.iry

QUANTITATIVE

ESTIMATION ON PAPER

OF HALOGENATED CHROMATOGRAMS

>I

H

HASHM

West Regro#cal Luboralovws.

ORGANIC

31at. 1957

ACIDS

t

C S 1.R , Lahove (Pahcslat,)

A simple and accurate method is described for the quantltatlve estimation of halogenated organic acids on paper chromatograms Promo- and lodo-acids could be estlmated accurately 3 98% by this method. The procedure for the quahtative separation of these acids on paper chromatograms was described in a previous papeP. EXPERIMENTAL Malevrals Propanol ww purlfmd by dlstlllatlon The conccntratcd ammonia was A.R. grade (s g o 088) 0 1% solution of eobin and 1% solution of diiodod~mcthylfluorcvceln rn 7o”A, v/v aqueous alcohol wcrc prcparcd by methods similar to wcrc used a~, odsorptlon lndlcators * Bromo- and iodo-acitlu those a~ dcscrbcd in a previous paper’ AQQararus and Qvocedrcvc Whatman’s No 4 filter paper purl fled by chromatographlc washu@ with 2N acctlc acids, dlstlllcd water and ION ammonia was used throughout The acds wm dtasolvcd in dllutc aqueous nmmontn. and the rcsultmg solution of thclr ammonium salts was apphcd to the chromatograms with a micropipette A convenient one may be made in ttic laboratory J. Tha ttcvclopmg solvent contalncd 70% propanol and 300/;,conccntrnted ammonia A “guldc” chromatogram was always run alongside the main chromatogram and tha position of the ac~dv was located only on the guldc chromatogram by tho procedure of HASMMI AND CULLIS* 4 and 5 c(g IS the detection limit for bromo- and lodo-acids re9pectlvely Tho acids on the main chromatogram was located by comparlvon to a gu~do chromatogram The ptcca of paper contalmng the ammomum salts of the acid was cut out of the chromatogram and rofluxcd for about 2 hours In a 250 ml flask with 20 ml of absolute alcohol and 1-2 g of motalhc sodium with occastonal shaking of the flask’* 6 The products wcro aIlowed to cool and were diluted by cautious addition of water through the condenser, I ml at a tlmc being added at first until tha vigorous action has ceiucd The total volume of the aolutlon ehould not exceed 50 ml. The solution, whlla kapt cool with tap water, was ncutrahsed with 6ZV halogen-free mtrlc acid using phenolphthalein as mdlcator, and a further 5 ml of acid were then added The halogons were dotarmmed Rafevences Q 107