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Investigation of chemical separation methods for Ca and Sr.
VOL. 16 (x957)
M ICI~O-~~O~U~fETRSC
DETERMINATION
OF ;\IElIGUIIY
w
Separation tnctttods for Ca and Sr in mixtures of both elements are nurncrous, Most are based on the estraction of the tlry nitrates with suitable solvents, while some use separation by selective l~~ecipitation as nitrates, sulfates, ferrocyanidcs or chromates. Ethyl alcohol, isobutyl alcohol, $z-bntyt alcohol-r-glycoi ether and acctont: have been investigated as solvents for the cstraction of Ca(NQ,), from the dry nitrate mixture. RAWSON’ described the separation of the nitrates using nitric acid of density r-46. FRESE?~‘KIS* and No~ti used a r : I ethyl aicoho~-ether mixture, while BROWNING~studied the separation by adding isoamyl alcohol to the saturated solution of the nitrates and subsequent boiling. Methods for the separation of carbonates using nitric acid, of sulfates using bitartrate, of chlorides with It-butyl alcohol saturated with hydrochloric acid, and of chromates with acetone-water and ethyl alcohol-water mixtures are also reported,, Rsferences
p.
320 .
VOL.
16
SEP,\RATION
(x957)
AND
METHODS FOR Ca
!%
313
dissolves. If, howcvcr, nitric acid of density greater than r..+G is used, the calcium nitrate is not readily dissolved and a considerable amount is weighed as Sr(NO,),. The separated Ca fraction however is practically free from Sr. Preliminary csperimcnts showccl that considerable amounts of Sr(NO,), arc dissolved together with the Ca(NO,),, if the digestion was carried out in a beaker covcrecl by a watch glass. This is obviously caused by evaporation of tllc nitric acid by the digestion in open vcsscl. However, by digesting the nitrate misturc in a desiccator, containing either nitric acicl of the same density as tlrc one used for digestion, or dry CaCI,, improved results wcrc obtained, even if the cligcstion was con tinucd for sexyera days.
:\
I 00 111~ zilicluot
c:vapc)rzitcd room
ghss ant1 the
IJI ;i cnlciurll/strulltil1111 mi.xtlire (as nitrates). containing ~‘“Ch as trxcr. is trcatctl will1 20 ml nitric. acitl (tl = 1 ..+C,) and tligcstctl for one thy at ‘L’hc prccipitatc is trat~sfcrrccl to il wciglictl in a clcuiccator containing tlry Cdl,.
to tlrvncss.
tcnipcrnturd
filter, wasl~ctl with wciglwtl. ;\n :dicliiot (:a-cont~inliri;ltic,rl.
Jn another
scrics
LO inl nitric acid (tl of tllis larccil>itiLtc
is moi~ntcrl
ccxltaining
of cspcrimcnts,
anillysctl rdioinctrically for ‘l‘hc results ill% sumiiurizctl
1..lG) iii
c
____ ____
(‘a hsn __ _.____.._...- ._._- .. .._..-......_ -_.. -._ -_._.-._._--..--.-
Sunrf’lc
._..._. -.-_..-
_..
err ,#,fi
013
Crmt~o~8itmliot8
;iftcr
19.9s
SO.CJ
7R.4
0.17 --_
.jCJ.”
.jl.G
0.7X
.1g*;! HO.O X0.2
*sI .(J ‘?O.‘.!
1 5 ..i
-.-
filtriltc:
c\*ill>c~r:ltioll
illlcl
01
was ;ws;lyccl tlrying.
for
c‘;L :ltltl
1
Sr ~I’I’II NImIc ACID, tl = _._ __._ ..-._ ..--- __. ,._ _ _.-.-.-_. ____.
,.._. ._. ____-._-__--___--_ Sr u,fi Ch ill .Sr(.VU.), urfl -----
20.3
tllc
Sr-tracer,
Sr-curitnrliinati(,ll, in ‘I’al)lc 1.
‘I’r\llL,IC SILI~,~HA~~ION
sinall pmtions. tlrictl for 2 Iioiirs at 130% I01 ratlionwtric counting tc) tlctcrnliiw
scprtrdrd
/mcliml~
.__. -_-._-.-.-_---_._Sr Ir1 Cll~NO,),
-_ 0.3 I -_ 0.30
I.7
-
-
0.2’
._-. __ ,,rg
I..IG
_.____. .___._. _. -__.. ..-_.--.-. -..Cu ‘Yo
99~ 15 -
$S.‘{ 07.C) -
AkC0VCr.V
_ SI ‘:!,
-.‘JCJ.f-1
_WI.3 rjs.cj
Thcsc results slrow that a quantitative separation is not obtained. The amount of Ca(NO,), remaining in the prccipitatc increases with the weight of Ca(NO,), in the misturc, whcrcas the dissolved amount of Sr(NO,), remains fairly constant. Accurate gravimctric results are accidentally obtained by compensation of errors. IZxlvaclio~tcof Lhc dry nilvales
wilh
ether-cLkyL alcohol
The separation of Ca and Sr by cstraction of the dry nitrates with cthcr-ctllyl alcohol 1 : I mixture, as described by l~~~s~~xrus~ is the method which has been most applied and is recorded in all classical handbooks of analytical chemistry. NoI_I.~ strcsscd the importance of traces of water in the mixtures of nitrates, as well as in the solvents, and proposed a slightly modified procedure. Preliminary gravimetric espcriments confirmed the statements of NOLL and showed that reliable results are obtained with macro-amounts of I : I mixtures, if care is taken to avoid all traces of water. 130th the methocl of I~IWSENIUS and the modified procedure according to NOLL IiTefcrcnces
p.
320
G.
3x4
I_EI,IA~lC’l-,J. EECliiiAUT
VOL.
16
(x957)
have been checked by tracer technique. Absolute alcohol and sodium dried ether were used. Extraction and filtration took place in a gloved box, containing silica gel. It appeared that NOLL’S method gave slightly better results.
A 100 nip Ca-Sr nitralc mixture is tlrictl at I 709a1:constant wciyllt.‘I’llc dry mixture is pulverizCd and digCstcd with .) 1111ethyl dCOhrJ~ at rtmln tcmlxxilturc. After 2 Iwurs 4 ml ether arc ncldcd ‘I’hc WhOk! pmccss takes@acu in a gloved box. Tlrc? and the tligwtion continued ovcrniglit. strontium nitrate is finally filtcrctl off, wuuhcrl will1 albsolutc alcollol-ctlwr mixture and dried. It is tcstctl for C;L-cotit~ltniri;~ti~jIl wlicrwts tlic? filtrate in i~tIillyWt1 fur Sr-cnntalninntion iw above. The rceultv arc givc!n in ‘I’:tl)lc I I.
SltI*hl~h’FlON m--m__-
-
-.-..--__--.--Cc1 ,,rg
-._.__..._ .--
SW,:/&
017
Cir
.-__._-.--5.1 ,r,l:
._-- -... ..- ._._.__-
19.5
,Z<).G 50.6 5”.3 80.3 77.0
___.._
AND ___...
Sr
I3Y I~,X’TI
__- ...__- ..____
_.- _._. _.-...-_
0.1.5
52.7 52.2
0.4 -
21 *.T
0.g
“1. I
I?‘ClllSH-ISTFIYL ._.---------
L;o~8trrdttrit io#rr,l sr~u*rtlrtlfractions ._._- ..__.______.__ --_-_-.-_.._-__----.-_ Cu it, Sr(NO.), wg Sr it1 Cu(NO,), r,r#
75.8
81.0
WI’Cli
..-
--
.,.. -_--_-_-_____-__---_~_
O.lC)
-0.5 _.._
0.0
ALCOIIOL
Kecouery CN %
sryz
99.“5
99.77
-
99.2
-.-
gx.g
-
1
-
-
gg.02 -
95.9
From thcsc results it appears that lin~sr~Nrus’ method, modified according to NOLL, yields no better results than RAWSON’s. Owing to the simplicity of the experimental procctlurc the latter has to bc preferred, the more that Sr(NO,),, as stated by CC’~LLAIZDAND Go~DSIJI~ED~, and more recently by KOHE AND MOTSCH~~, forms a gelatincous precipitate in organic solvents and is less readily filtered.
BROWNING~ describes the separation of Ca and Sr with isoamyl alcohol (B.P. 128”). After acldition of IO to 30 ml of solvent to a saturated aqueous solution of the nitrates, the liquid is boiled, expelling the water present. Ca(NO,), goes into solution whereas insoluble Sr(NO:,), separates. Quantitative results have not yet been communicated. According to the solubility date of SEIDELL~~ isoatnyl alcohol should give a better separation than most other organic reagents, Preliminary cxpcriments, however, have shown that a quantitative removal of the water by boiling the solution is not feasible. This causes incomplete precipitation of the strontium nitrate, and also considerable contamination of the latter with Ca occurs. Sr(NO,,), can be obtained in a fairly pure state after double extraction, but the quantity dissolved also increases. The procedure is less time-consuming than the preceding ones. The filtration however is more difficult. Experimental results are given in ‘Tnblc IT 1. Ihferetlces
p.
320
16 (1957)
VOL.
_._ .----
-
SEPARATION
.___----_-_-_-
ISXTHACTION .__.--_-----
OF
THE
METHODS
FOR
h’ITRATBS
WITH
Ca AND
Sr
ISOANYL ALCOHOL ---___.-__.__.--
CoWwtitmlio~t o/ sepuralcJ /ruclims -. --._-.. ___--_ -- --.. --_---_---_---___-.-.--Sr it8 Cu(h’O,),” wg Sr ,,rg Cu it; Sr(dVvO,),b ,,rg ___-- .._.-_- ._._.__.^-.____ -.._.-.. ..- -.___ _ . ..--. - _.-....-.-... --.__-.-
.___ -_-_--_-.-----_. Cn ,ng -__-__-2
)0..l
79.7 Hi.7
0. I -
52.4
50.0
0.5
49.7 78.x Ho.0
50.9 21.1 21.2
I .cJ
__.- ___._ - ...._-__$1 after
sin&
IJ ilftcr
c\~l~lJk!
-_
99.3’
--
99.“5 .-
97.8 -_
09.78 -
0.45
_. .__....._. . .-... _.
_-
99.54
1.1 -
0.17 -
..._._._. - ..._.. ._
-_.._ ..-_--_ Cu” “/o ._..._.___ __ ___..___. ._____ ..:‘:r;.:.’
O..# --
--
-_.__.
Recovery --.-.
Sanlple
-..-._ - ._.._. .- .
. -
97.0
. .
_. _. _ _._ ______
cxtrnction cstrikctioll
From these results it appears that I: to 2O/o of the Sr(NO,), remains in the so11 after one cstraction, whereas 0.2 to I”/; of calcium is still present in the stron fraction after 2 cstractions. Sclectivc
01 SY(NO,),
/mxifdatio~t
zedh
HNO,
B~;ecl on the study of the influcncc of the nitric acid concentration on the bility of the Ca and Sr nitrates, \VILIARD AND GOODSPISEI~” obtained a good scpar; of both clcmcnts from L : I misturcs by adding HNO,, cl =-: I.~c, to a dil nitric acid solution, until the final density reaches a value of r.45. before filtr; the precipitate of Sr(NO,), is left r to 2 hours in contact with the solution in a c vessel. For less favourable ratio’s of Ca : Sr double precipitation is recommer The nitric acid should be added dropwise under vigorous stirring. Radiochemical investigation of this method has shown that the separatic Results communicated in Tab1 never quantitative after a single precipitation. show that a very pure precipitate of Sr(NO,), is obtained after double prccipita
__.-._-__-.
__.-^-
SI:I~AH,\~I’ION
__. - .._._.. .__..._-..._...__..---.-SlWlpk
CC8 rug __.._..__._..-_
.-.-._.-_-.-___-.-_----
single C~CJIIIJIC
PveciPitrction
IINO, _-.-.._ - --._ - _.__ _-._.-. rtecowy
Sr itr Ca(rVO,),c’ mg ._.. . --.._ .-.--.-.
Sr rng Gr in Sr(NO.),b wrfi ._.._._-_.-_- ___.._._ _ _..___ ..-... -..--_ - -.-
-----1____1
$1 after IJ after
IVY SISLI~TIVIS I’l~bxIwT,\‘rIoN wvrIf .._ -_._--.----.-.-_ -___-.-.-.-.--.- -_.Co~hwrinafiw8 of scpuralJ /mcliom
-.-._._
-
.._..
-_---_
.
.
_....-.
c,&
-
--...
.-
-.
.-.-
I::, _.. . . .._ _
.--
.._.
_._..
S?” ..-..
_.
._...
prccipitntion precipitation
from ltonwgemo~hs sol&ion
A separation method based on the selective precipitation of S&O, from h gcneous solution, using dimethyl sulfate, has been described by ELVING AND ATTA~ using the following procedure: 25 ml of a solution of the mixed nit containing Ca or Sr tracer, are treated with 20 ml of methyl alcohol and 0.5 Itefcremes
p. 320
ZIG
G. IXLIAERT,
J. EECKI-IAUT
VOL.
16 (x957)
(CI-l,),SO,I for each ro mg quantity of Sr present. After thorough mixing, the solution is heated at about Go%. As the hydrolysis of (Ci-I,)2S0, proceeds, SrSO, gradually precipitates. After about I hour the precipitate has scttlcd and can be separated from the clear supcrnatant solution. ‘I’l~c results obtained arc summarized in ‘i’ablc V, showing that the SrSO, prccipitation is not quantitative if a large amount oi Ca is present.
TIw influc*ncc of the amount of added reagent has been invcstigatcd in a special series of cspcrimcnts. Solutions containing 20 1176’ of Sr and 80 mg of Ca wcrc treated rcspcctivcly with I, 2 and 5 ml rcagcnt. In cacll case the amount of Sr remaining in the solution :~ncl tlw amount of CaSO, coprccipitatcd with the SrSO,I wcrc detcrminccl by rncliocl~cmical tcchniqucs. Tlic results arc rcprcsented in Fig. I. It is obvious tllat tlic slight cx’ccss of reagent, ncccssary for tlicquantitative prccipitation of SrSO,, GLUSCS considerable coprccipitntion of CaSO,,. Hence this method cannot bc rccommcnded for the scparntion of Sr from Cain mixtures of unknown composition.
-C
ml (CH,),
SO.
VOL.
SEPARATION
16 (1957)
of
Selective preci+itiition
BIETHODS
Ca
FOR
AND
Sr
317
Sr us SrCrO,
There is little agreement in the literature concerning the value of the chromate precipitation method for the separation of Sr and Ca. DAVIS~ states that, on account of solubility data, a good separation should bc obtained, whereas FRESENIUS AND RIJPPERT~ found experimentally unreliable results. The method is based on the insolubility of SrCrO, in aqueous alcoholic solution. The solution of the Sr-Ca mixture is treated with K,C.rO,. heated at 6o”C, and ethyl alcohol is added for precipitation of SrCrO,. Fr~rmsslus AND I
SRPARATION
. .-. <:a
snmp1c ..
.
.-.
..--
sr
,,rg
20.1
. -.
.
,,I#
50.0
‘LX..) -
..-
. -
Sr
AND
Cot:/amDruf im of
in
.
-
SrCrO,
..- .-..
Sr
it,
cucro,
_,_._ -._-... - ._... .._.__.
_.
m,q
._.
of
-
__..
-
23.2 -
OS75 -
s.7 -
2.3 -
0.9
.._. _ ...__..___ __ __._ . ._
_
.___ Sr
.
.
a,;
92.3 --_ 92.0
-
HI.0 -.--_.-_--._-
D,\vrs
0.G
-
y,
98.3
4.1 ---_-.__--.---_-.-
I\‘tWWy _ .__.....
95.5 -
-
-_.--..
_
87.0 --
‘$. I
- .
. .
cat
-
I*.1 -_ . .
._. ..-..
SrCrO,
6.27 --
2.3 -
.
OF
scparalrd /rucfions .-.. -.. ._ ._ _... ._-.-
,,,g
I’roccdure
__-
.
I’HECIPITA’TION
-
I
83.2 82.8 SO.4 5r.G 2 4 *5 21.7
X9.3 X9.7 50.9 50.8 80.3 81.3
UY
24.4
81.3 49.8 51.1 20.
Gil
._. Ca
79.8
20.0 51.9 SO.5 80.9 .. . -.
OF
96.7 _98.5 97.1 -
72.0 83.1 9.5.8
___
CONCLUSIONS
RAWSON~
Among
all the methods investigated or \vith an ethyl alcohol-ether
Relerences
p. 320
the extraction with mixture according to
HNO, FRESENIUS~
according to gives the
3x8
G. LELIAERT,
J. EECKHAUT
VOL.
16 (1957)
most reliable results, although both methods give no cluantitativc separation. Hence the percentage error increases when the concentration ratio becomes less favourablc. It was found that a very pure Sr(NO,), fraction can be obtained by double precipitation with cont. HNO,, according to M’ILI_I\I~I) AND GooDsr~lzr@. Uesiclcs, it could be established that the extraction of the dry nitrates with HNO, of density d > 1.46 gives a Ca(NO,), fraction, practically free from Sr. These results have been used for the development of a new method.
DETERMINATION
01:
Sr ASD Ca IN ;Mtx*rukBs BY *rIfE Iso*roI’Ic I>II.UTION h~E.1’IlOU
‘I’l~c isotopic dilution mctllocl is based on the fact thilt, when a radiotraccr is added to a solution of its not active isotope, present in the precipitate formed by adding a suitable reagent to the solution is ecluul to their ratio in the solution before precipitation. It can be derived, when no active isotope is present in the original solution, that the weight Gs of the element sought is given by the relation: cJ.Y zzz (&
s t
s’,c
-
r
l-X/).
1
where : Gd: weight of tracer added Sd: specific activity of tracer addled S,:,q,.: specific activity of isolatcd~ precipitate ‘I’lrc mcthocl involves the isolation of tllc clement to be tletcrmincd wit11 a high degree of purity. Precipitation howcvcr ought not to be quantitative.
It was found that a fairly pure Sr(NO,,), can 1~ obtainccl by cloublc precipitation with concentrated I-IN 0,. Solubility clata of M’ILI.~\RD AE;D GOOIXW:I? 19 show that the density of HNO, shall be less than r.4G in orclcr to avoid coprccipitation of Ca. Although a cluantitativc precipitation is not necessary, a good yiclcl can be dcsirable, cspccially when small amounts of Sr arc to bc detcrminccl. ‘l’hercfore, the influence of the precipitation speed on the yield ancl the purit$ of the precipitated Sr(NO,), has been examined. The less favourable ratio Sr : Ca = 20 mg : 80 mg has been used in these espcriments, and HNO,, cl - 1.53, has been added until the density reached the vnluc cl = 1.45. Final \*olumc has been reduced to 30 ml in order to be able to apply the method to the clctcrmination of small quantities of Sr. In these conditions however some Ca(NO,), is prccipikltcd with the Sr(NO.&. The results are represented in Fig. 2. It can easily be seen that the time for precipitation sl~o~tlclbc at least 30 minutes.
Conditions
for t/u dctermi?tation
of Ctc
It has already been mentioned that practically no Sr(KO& dissolves in HNO, of density z=- 1.46 and a pure Ca(NO,), fraction can be obtained in this way, although the separation is not quantitative.
lh2fere~rccs p.
320
VOL.
16 (1957)
SEPARATION
METHODS
FOR Ca AXD
Sr
%Cc
to<
I
-----
t
1a6
0
1(
I.6 x4
I
10
35
100
-
Fig. 2. Influcncc of the precipitation T: Yield of Sr(NO,),, I I : ‘j;,Cn precipitated wit11 Sr(NO,),.
mln
time.
//-I: 15
60
2ZSi-l
Fig. 3. Influence of tlzc extraction 1: Yicltl uf Ca(NO,)s, 11: Pruccnt Sr dissolved.
time.
Experiments were drawn in order to determine the influence of the extraction time on the yield and the purity of the Ca(NO,), obtained, using HNO,, d = 1.468. The results obtained for the less favourable ratio Ca : Sr = 20 mg : 80 mg are drawn in Fig. ;j. It is obvious that the best results are obtained when the extraction time is short. Extraction for 1.5 min is to be recommcndcd.
13nscd on the above cxpcrimcnts the following procedure has been izclopted: To a neutral mixture of calcium ant1 strontium nitratcs,a known amount of tracer Sr and Ce is added. After homogeneisation, HNO,, d =I 1.5 I, is adtlcd dropwisc under vigorous stirring until the final density rcachcs the value. tl = I .45, this taking about 30 to 40 zninlztcs. The Sr(NO,), precipitate is filtered off, The pure precipitate is filtered, washed with rcdissolvcd and purified by double precipitation. I-INO,, d = r.45, rlricd at 135~. and wcighcd as strontium nitrate. ‘fhc filtrate is evaporated to dryness. The residue is digested with IO ml PINO,, d = I .4(i8, for z 5 min and filtered. The filtrate, containing pure Clr(NO,), is evaporated to clryncss in ,thc prcsencc of an excess of sulfuric acid ant1 the resicluc is wcighcd as CaS?,. From the activities of a knowzz weight of each pure fraction, and of the pure tracer added, speczfzc activities can be computed azid the percentage of Sr and Ca can be calculated with the above forznula.
The procedure has been checked on a semi-micro scale with Ca-Sr mixtures I : I of total metal content of about 20 mg, weights being determined on the microbalance. Owing to the small weights of samples correction for self-absorption could be avoided when the measured weights of precipitate and of tracer were nearly equal. The results obtained by this method are shown in Table VII. It can be seen that the accuracy obtained with 20 mg samples is comparable that obtained by the best gravimetric methods with zoo mg samples. Referemes
.p. 320
with
16 (1957)
VOL.
__-_ - -....
DIS’CISRMINATIOS ._---.-.
Sulllple
__._
_.__ _ ___
.._
OIZ c:L .___... ___..
ST ,_____ ..__._ .._.__--.
I
.._
..-
BY Ttll: ISOTOPIC DILUTI0.V _._- -- .__-. -... _..w._ e-.-p
hIIST:101> ----.----.._-_
nrji /rmwl
_
_.___
.-.
II
ANU $I’ IN ~1IX’rUl~I~S _ .__. _ __.__._._. _- .__.._.. ..__
r,rg presolf
Cu _. __ _..__..
..-.-_-.
.SI
----.-
“/
__ ___ ._. _ . _ CC& sr --.-.-- ..--. -.-_I.___. ------.
.1Aif)
‘1.12
.5*(‘5
4 ~23
5.025
.1.18
5.145
4
83.1
.c*m,
_
. . .._._.
-I_ 3.2 --I. 2..1
CO _._._ . . _
+ 2.6 -1.3.6
‘I’llc cllli\l~tit;lti\~c sq):rr;tt.icJn of C’a xntl Sr by 511nlo of tllc IllIIst iritcrcsting cllcinical priJccIlIIrcs IL coliltl Lc sliown that nIJ satisIias I~ccri invcstifptccl, Iising rniliidicIiiic:~l tracer tcclinicliicn. fi~ctory scp~mtion ci~ul~l 1112 acliicvcd ;mtl ~:ooil rcslilts xrc olkiinctl in Some cilscs IJY compcnsi~tion of
errors.
‘I’lic rcnults Iii~vc: been Iiscil for tlw ilcvcliq~mc:nt ul :tli isotcq)ic ilililtion niutliotl for tllc rlctcrIniiiatic,n of <‘:L and Sr iii nlixtiircs uf tlicir SilltS. licli:L!h results we c~l~ttliiiotl on tlic scmi-microSCillC.
. IA
Si.lXtriLtic~ll
iIltJrcSSiLlltCS
nc
pcrtnct
ilii a
Gt.6
d’obtcnir
calcium
ct
i:tucli& Ilnc
illI
tlu llloycll
Sdparntion
l.cBslrMli
strontiiini 1xir ~1iii:lfliic!s-iilics ilcs liiStliotlcs J”(::l ct n”Sr. II S’cSt adr6 tics tribxllrs quWltitittiVc,
IlliliS
c\Il’~~ll olItic:nC
sou\‘cllt
cliiiniclucs C1ll’iLllCllllC! dcs
Its
plus
IIlIXlIotlc
l+dSUltiltS
satis-
f;iisniits pr compcnsik.tion tics crrciirs. 1.~4 rdsultrrts ant pcrmis tI’~tnl~lir iiilc nouvcllc in~tllotlc ])iLr cliliiticm isl>tcq>icluo pour In ddtcrS;ltiSfiliSnIlts Ollt dtc’ niination ties dcux LclJnicnts tlritis iin ni&lnii~c tic Icurs sols. IhS l+Slllti~tS 0lJtcIiIIs h l’~clicllc scmi-micro.
Eiiiigc tlcr gcbr!iucl~liclistcn clicniisclicn Mctlicxlcn znr ‘L’rcnnunK \‘on CillCilllll untl Strontium wurclcii wit I-lilfc tlcr Isotopcn 4nC;L iiiicl Wr rlntcrsclcht. Iis zcij+c sich tlass cinc cllli~lltit:lti~~e ‘h-cnniing nicnialu 211 crkliircn sind.
crfolgt
Iilitl giitc
~riLviriicLrisclic
I~CSllltiltC
vicllciclit
tlIlrclI
I~cllll~rl<~Jlllpcllsiltioll
IXc Ergcbnissc tlicscr 1~xpcrinwnt.c crlaubtcn tlic Ihtwicklun~ cincr luotoI,cllvcrtliinnrin~smcthorlc fiir clic Hcstinlrnung van Ca untl Sr in ihrcn Snlzgcn~isclwn. In1 Scminlikro-13crcich wiirdcn bcfriccligcriclc Resilltatc crhnltcll.
M ICI~O-~~O~U~fETRSC
DETERMINATION
OF ;\IElIGUIIY
w
Separation tnctttods for Ca and Sr in mixtures of both elements are nurncrous, Most are based on the estraction of the tlry nitrates with suitable solvents, while some use separation by selective l~~ecipitation as nitrates, sulfates, ferrocyanidcs or chromates. Ethyl alcohol, isobutyl alcohol, $z-bntyt alcohol-r-glycoi ether and acctont: have been investigated as solvents for the cstraction of Ca(NQ,), from the dry nitrate mixture. RAWSON’ described the separation of the nitrates using nitric acid of density r-46. FRESE?~‘KIS* and No~ti used a r : I ethyl aicoho~-ether mixture, while BROWNING~studied the separation by adding isoamyl alcohol to the saturated solution of the nitrates and subsequent boiling. Methods for the separation of carbonates using nitric acid, of sulfates using bitartrate, of chlorides with It-butyl alcohol saturated with hydrochloric acid, and of chromates with acetone-water and ethyl alcohol-water mixtures are also reported,, Rsferences
p.
320 .
VOL.
16
SEP,\RATION
(x957)
AND
METHODS FOR Ca
!%
313
dissolves. If, howcvcr, nitric acid of density greater than r..+G is used, the calcium nitrate is not readily dissolved and a considerable amount is weighed as Sr(NO,),. The separated Ca fraction however is practically free from Sr. Preliminary csperimcnts showccl that considerable amounts of Sr(NO,), arc dissolved together with the Ca(NO,),, if the digestion was carried out in a beaker covcrecl by a watch glass. This is obviously caused by evaporation of tllc nitric acid by the digestion in open vcsscl. However, by digesting the nitrate misturc in a desiccator, containing either nitric acicl of the same density as tlrc one used for digestion, or dry CaCI,, improved results wcrc obtained, even if the cligcstion was con tinucd for sexyera days.
:\
I 00 111~ zilicluot
c:vapc)rzitcd room
ghss ant1 the
IJI ;i cnlciurll/strulltil1111 mi.xtlire (as nitrates). containing ~‘“Ch as trxcr. is trcatctl will1 20 ml nitric. acitl (tl = 1 ..+C,) and tligcstctl for one thy at ‘L’hc prccipitatc is trat~sfcrrccl to il wciglictl in a clcuiccator containing tlry Cdl,.
to tlrvncss.
tcnipcrnturd
filter, wasl~ctl with wciglwtl. ;\n :dicliiot (:a-cont~inliri;ltic,rl.
Jn another
scrics
LO inl nitric acid (tl of tllis larccil>itiLtc
is moi~ntcrl
ccxltaining
of cspcrimcnts,
anillysctl rdioinctrically for ‘l‘hc results ill% sumiiurizctl
1..lG) iii
c
____ ____
(‘a hsn __ _.____.._...- ._._- .. .._..-......_ -_.. -._ -_._.-._._--..--.-
Sunrf’lc
._..._. -.-_..-
_..
err ,#,fi
013
Crmt~o~8itmliot8
;iftcr
19.9s
SO.CJ
7R.4
0.17 --_
.jCJ.”
.jl.G
0.7X
.1g*;! HO.O X0.2
*sI .(J ‘?O.‘.!
1 5 ..i
-.-
filtriltc:
c\*ill>c~r:ltioll
illlcl
01
was ;ws;lyccl tlrying.
for
c‘;L :ltltl
1
Sr ~I’I’II NImIc ACID, tl = _._ __._ ..-._ ..--- __. ,._ _ _.-.-.-_. ____.
,.._. ._. ____-._-__--___--_ Sr u,fi Ch ill .Sr(.VU.), urfl -----
20.3
tllc
Sr-tracer,
Sr-curitnrliinati(,ll, in ‘I’al)lc 1.
‘I’r\llL,IC SILI~,~HA~~ION
sinall pmtions. tlrictl for 2 Iioiirs at 130% I01 ratlionwtric counting tc) tlctcrnliiw
scprtrdrd
/mcliml~
.__. -_-._-.-.-_---_._Sr Ir1 Cll~NO,),
-_ 0.3 I -_ 0.30
I.7
-
-
0.2’
._-. __ ,,rg
I..IG
_.____. .___._. _. -__.. ..-_.--.-. -..Cu ‘Yo
99~ 15 -
$S.‘{ 07.C) -
AkC0VCr.V
_ SI ‘:!,
-.‘JCJ.f-1
_WI.3 rjs.cj
Thcsc results slrow that a quantitative separation is not obtained. The amount of Ca(NO,), remaining in the prccipitatc increases with the weight of Ca(NO,), in the misturc, whcrcas the dissolved amount of Sr(NO,), remains fairly constant. Accurate gravimctric results are accidentally obtained by compensation of errors. IZxlvaclio~tcof Lhc dry nilvales
wilh
ether-cLkyL alcohol
The separation of Ca and Sr by cstraction of the dry nitrates with cthcr-ctllyl alcohol 1 : I mixture, as described by l~~~s~~xrus~ is the method which has been most applied and is recorded in all classical handbooks of analytical chemistry. NoI_I.~ strcsscd the importance of traces of water in the mixtures of nitrates, as well as in the solvents, and proposed a slightly modified procedure. Preliminary gravimetric espcriments confirmed the statements of NOLL and showed that reliable results are obtained with macro-amounts of I : I mixtures, if care is taken to avoid all traces of water. 130th the methocl of I~IWSENIUS and the modified procedure according to NOLL IiTefcrcnces
p.
320
G.
3x4
I_EI,IA~lC’l-,J. EECliiiAUT
VOL.
16
(x957)
have been checked by tracer technique. Absolute alcohol and sodium dried ether were used. Extraction and filtration took place in a gloved box, containing silica gel. It appeared that NOLL’S method gave slightly better results.
A 100 nip Ca-Sr nitralc mixture is tlrictl at I 709a1:constant wciyllt.‘I’llc dry mixture is pulverizCd and digCstcd with .) 1111ethyl dCOhrJ~ at rtmln tcmlxxilturc. After 2 Iwurs 4 ml ether arc ncldcd ‘I’hc WhOk! pmccss takes@acu in a gloved box. Tlrc? and the tligwtion continued ovcrniglit. strontium nitrate is finally filtcrctl off, wuuhcrl will1 albsolutc alcollol-ctlwr mixture and dried. It is tcstctl for C;L-cotit~ltniri;~ti~jIl wlicrwts tlic? filtrate in i~tIillyWt1 fur Sr-cnntalninntion iw above. The rceultv arc givc!n in ‘I’:tl)lc I I.
SltI*hl~h’FlON m--m__-
-
-.-..--__--.--Cc1 ,,rg
-._.__..._ .--
SW,:/&
017
Cir
.-__._-.--5.1 ,r,l:
._-- -... ..- ._._.__-
19.5
,Z<).G 50.6 5”.3 80.3 77.0
___.._
AND ___...
Sr
I3Y I~,X’TI
__- ...__- ..____
_.- _._. _.-...-_
0.1.5
52.7 52.2
0.4 -
21 *.T
0.g
“1. I
I?‘ClllSH-ISTFIYL ._.---------
L;o~8trrdttrit io#rr,l sr~u*rtlrtlfractions ._._- ..__.______.__ --_-_-.-_.._-__----.-_ Cu it, Sr(NO.), wg Sr it1 Cu(NO,), r,r#
75.8
81.0
WI’Cli
..-
--
.,.. -_--_-_-_____-__---_~_
O.lC)
-0.5 _.._
0.0
ALCOIIOL
Kecouery CN %
sryz
99.“5
99.77
-
99.2
-.-
gx.g
-
1
-
-
gg.02 -
95.9
From thcsc results it appears that lin~sr~Nrus’ method, modified according to NOLL, yields no better results than RAWSON’s. Owing to the simplicity of the experimental procctlurc the latter has to bc preferred, the more that Sr(NO,),, as stated by CC’~LLAIZDAND Go~DSIJI~ED~, and more recently by KOHE AND MOTSCH~~, forms a gelatincous precipitate in organic solvents and is less readily filtered.
BROWNING~ describes the separation of Ca and Sr with isoamyl alcohol (B.P. 128”). After acldition of IO to 30 ml of solvent to a saturated aqueous solution of the nitrates, the liquid is boiled, expelling the water present. Ca(NO,), goes into solution whereas insoluble Sr(NO:,), separates. Quantitative results have not yet been communicated. According to the solubility date of SEIDELL~~ isoatnyl alcohol should give a better separation than most other organic reagents, Preliminary cxpcriments, however, have shown that a quantitative removal of the water by boiling the solution is not feasible. This causes incomplete precipitation of the strontium nitrate, and also considerable contamination of the latter with Ca occurs. Sr(NO,,), can be obtained in a fairly pure state after double extraction, but the quantity dissolved also increases. The procedure is less time-consuming than the preceding ones. The filtration however is more difficult. Experimental results are given in ‘Tnblc IT 1. Ihferetlces
p.
320
16 (1957)
VOL.
_._ .----
-
SEPARATION
.___----_-_-_-
ISXTHACTION .__.--_-----
OF
THE
METHODS
FOR
h’ITRATBS
WITH
Ca AND
Sr
ISOANYL ALCOHOL ---___.-__.__.--
CoWwtitmlio~t o/ sepuralcJ /ruclims -. --._-.. ___--_ -- --.. --_---_---_---___-.-.--Sr it8 Cu(h’O,),” wg Sr ,,rg Cu it; Sr(dVvO,),b ,,rg ___-- .._.-_- ._._.__.^-.____ -.._.-.. ..- -.___ _ . ..--. - _.-....-.-... --.__-.-
.___ -_-_--_-.-----_. Cn ,ng -__-__-2
)0..l
79.7 Hi.7
0. I -
52.4
50.0
0.5
49.7 78.x Ho.0
50.9 21.1 21.2
I .cJ
__.- ___._ - ...._-__$1 after
sin&
IJ ilftcr
c\~l~lJk!
-_
99.3’
--
99.“5 .-
97.8 -_
09.78 -
0.45
_. .__....._. . .-... _.
_-
99.54
1.1 -
0.17 -
..._._._. - ..._.. ._
-_.._ ..-_--_ Cu” “/o ._..._.___ __ ___..___. ._____ ..:‘:r;.:.’
O..# --
--
-_.__.
Recovery --.-.
Sanlple
-..-._ - ._.._. .- .
. -
97.0
. .
_. _. _ _._ ______
cxtrnction cstrikctioll
From these results it appears that I: to 2O/o of the Sr(NO,), remains in the so11 after one cstraction, whereas 0.2 to I”/; of calcium is still present in the stron fraction after 2 cstractions. Sclectivc
01 SY(NO,),
/mxifdatio~t
zedh
HNO,
B~;ecl on the study of the influcncc of the nitric acid concentration on the bility of the Ca and Sr nitrates, \VILIARD AND GOODSPISEI~” obtained a good scpar; of both clcmcnts from L : I misturcs by adding HNO,, cl =-: I.~c, to a dil nitric acid solution, until the final density reaches a value of r.45. before filtr; the precipitate of Sr(NO,), is left r to 2 hours in contact with the solution in a c vessel. For less favourable ratio’s of Ca : Sr double precipitation is recommer The nitric acid should be added dropwise under vigorous stirring. Radiochemical investigation of this method has shown that the separatic Results communicated in Tab1 never quantitative after a single precipitation. show that a very pure precipitate of Sr(NO,), is obtained after double prccipita
__.-._-__-.
__.-^-
SI:I~AH,\~I’ION
__. - .._._.. .__..._-..._...__..---.-SlWlpk
CC8 rug __.._..__._..-_
.-.-._.-_-.-___-.-_----
single C~CJIIIJIC
PveciPitrction
IINO, _-.-.._ - --._ - _.__ _-._.-. rtecowy
Sr itr Ca(rVO,),c’ mg ._.. . --.._ .-.--.-.
Sr rng Gr in Sr(NO.),b wrfi ._.._._-_.-_- ___.._._ _ _..___ ..-... -..--_ - -.-
-----1____1
$1 after IJ after
IVY SISLI~TIVIS I’l~bxIwT,\‘rIoN wvrIf .._ -_._--.----.-.-_ -___-.-.-.-.--.- -_.Co~hwrinafiw8 of scpuralJ /mcliom
-.-._._
-
.._..
-_---_
.
.
_....-.
c,&
-
--...
.-
-.
.-.-
I::, _.. . . .._ _
.--
.._.
_._..
S?” ..-..
_.
._...
prccipitntion precipitation
from ltonwgemo~hs sol&ion
A separation method based on the selective precipitation of S&O, from h gcneous solution, using dimethyl sulfate, has been described by ELVING AND ATTA~ using the following procedure: 25 ml of a solution of the mixed nit containing Ca or Sr tracer, are treated with 20 ml of methyl alcohol and 0.5 Itefcremes
p. 320
ZIG
G. IXLIAERT,
J. EECKI-IAUT
VOL.
16 (x957)
(CI-l,),SO,I for each ro mg quantity of Sr present. After thorough mixing, the solution is heated at about Go%. As the hydrolysis of (Ci-I,)2S0, proceeds, SrSO, gradually precipitates. After about I hour the precipitate has scttlcd and can be separated from the clear supcrnatant solution. ‘I’l~c results obtained arc summarized in ‘i’ablc V, showing that the SrSO, prccipitation is not quantitative if a large amount oi Ca is present.
TIw influc*ncc of the amount of added reagent has been invcstigatcd in a special series of cspcrimcnts. Solutions containing 20 1176’ of Sr and 80 mg of Ca wcrc treated rcspcctivcly with I, 2 and 5 ml rcagcnt. In cacll case the amount of Sr remaining in the solution :~ncl tlw amount of CaSO, coprccipitatcd with the SrSO,I wcrc detcrminccl by rncliocl~cmical tcchniqucs. Tlic results arc rcprcsented in Fig. I. It is obvious tllat tlic slight cx’ccss of reagent, ncccssary for tlicquantitative prccipitation of SrSO,, GLUSCS considerable coprccipitntion of CaSO,,. Hence this method cannot bc rccommcnded for the scparntion of Sr from Cain mixtures of unknown composition.
-C
ml (CH,),
SO.
VOL.
SEPARATION
16 (1957)
of
Selective preci+itiition
BIETHODS
Ca
FOR
AND
Sr
317
Sr us SrCrO,
There is little agreement in the literature concerning the value of the chromate precipitation method for the separation of Sr and Ca. DAVIS~ states that, on account of solubility data, a good separation should bc obtained, whereas FRESENIUS AND RIJPPERT~ found experimentally unreliable results. The method is based on the insolubility of SrCrO, in aqueous alcoholic solution. The solution of the Sr-Ca mixture is treated with K,C.rO,. heated at 6o”C, and ethyl alcohol is added for precipitation of SrCrO,. Fr~rmsslus AND I
SRPARATION
. .-. <:a
snmp1c ..
.
.-.
..--
sr
,,rg
20.1
. -.
.
,,I#
50.0
‘LX..) -
..-
. -
Sr
AND
Cot:/amDruf im of
in
.
-
SrCrO,
..- .-..
Sr
it,
cucro,
_,_._ -._-... - ._... .._.__.
_.
m,q
._.
of
-
__..
-
23.2 -
OS75 -
s.7 -
2.3 -
0.9
.._. _ ...__..___ __ __._ . ._
_
.___ Sr
.
.
a,;
92.3 --_ 92.0
-
HI.0 -.--_.-_--._-
D,\vrs
0.G
-
y,
98.3
4.1 ---_-.__--.---_-.-
I\‘tWWy _ .__.....
95.5 -
-
-_.--..
_
87.0 --
‘$. I
- .
. .
cat
-
I*.1 -_ . .
._. ..-..
SrCrO,
6.27 --
2.3 -
.
OF
scparalrd /rucfions .-.. -.. ._ ._ _... ._-.-
,,,g
I’roccdure
__-
.
I’HECIPITA’TION
-
I
83.2 82.8 SO.4 5r.G 2 4 *5 21.7
X9.3 X9.7 50.9 50.8 80.3 81.3
UY
24.4
81.3 49.8 51.1 20.
Gil
._. Ca
79.8
20.0 51.9 SO.5 80.9 .. . -.
OF
96.7 _98.5 97.1 -
72.0 83.1 9.5.8
___
CONCLUSIONS
RAWSON~
Among
all the methods investigated or \vith an ethyl alcohol-ether
Relerences
p. 320
the extraction with mixture according to
HNO, FRESENIUS~
according to gives the
3x8
G. LELIAERT,
J. EECKHAUT
VOL.
16 (1957)
most reliable results, although both methods give no cluantitativc separation. Hence the percentage error increases when the concentration ratio becomes less favourablc. It was found that a very pure Sr(NO,), fraction can be obtained by double precipitation with cont. HNO,, according to M’ILI_I\I~I) AND GooDsr~lzr@. Uesiclcs, it could be established that the extraction of the dry nitrates with HNO, of density d > 1.46 gives a Ca(NO,), fraction, practically free from Sr. These results have been used for the development of a new method.
DETERMINATION
01:
Sr ASD Ca IN ;Mtx*rukBs BY *rIfE Iso*roI’Ic I>II.UTION h~E.1’IlOU
‘I’l~c isotopic dilution mctllocl is based on the fact thilt, when a radiotraccr is added to a solution of its not active isotope, present in the precipitate formed by adding a suitable reagent to the solution is ecluul to their ratio in the solution before precipitation. It can be derived, when no active isotope is present in the original solution, that the weight Gs of the element sought is given by the relation: cJ.Y zzz (&
s t
s’,c
-
r
l-X/).
1
where : Gd: weight of tracer added Sd: specific activity of tracer addled S,:,q,.: specific activity of isolatcd~ precipitate ‘I’lrc mcthocl involves the isolation of tllc clement to be tletcrmincd wit11 a high degree of purity. Precipitation howcvcr ought not to be quantitative.
It was found that a fairly pure Sr(NO,,), can 1~ obtainccl by cloublc precipitation with concentrated I-IN 0,. Solubility clata of M’ILI.~\RD AE;D GOOIXW:I? 19 show that the density of HNO, shall be less than r.4G in orclcr to avoid coprccipitation of Ca. Although a cluantitativc precipitation is not necessary, a good yiclcl can be dcsirable, cspccially when small amounts of Sr arc to bc detcrminccl. ‘l’hercfore, the influence of the precipitation speed on the yield ancl the purit$ of the precipitated Sr(NO,), has been examined. The less favourable ratio Sr : Ca = 20 mg : 80 mg has been used in these espcriments, and HNO,, cl - 1.53, has been added until the density reached the vnluc cl = 1.45. Final \*olumc has been reduced to 30 ml in order to be able to apply the method to the clctcrmination of small quantities of Sr. In these conditions however some Ca(NO,), is prccipikltcd with the Sr(NO.&. The results are represented in Fig. 2. It can easily be seen that the time for precipitation sl~o~tlclbc at least 30 minutes.
Conditions
for t/u dctermi?tation
of Ctc
It has already been mentioned that practically no Sr(KO& dissolves in HNO, of density z=- 1.46 and a pure Ca(NO,), fraction can be obtained in this way, although the separation is not quantitative.
lh2fere~rccs p.
320
VOL.
16 (1957)
SEPARATION
METHODS
FOR Ca AXD
Sr
%Cc
to<
I
-----
t
1a6
0
1(
I.6 x4
I
10
35
100
-
Fig. 2. Influcncc of the precipitation T: Yield of Sr(NO,),, I I : ‘j;,Cn precipitated wit11 Sr(NO,),.
mln
time.
//-I: 15
60
2ZSi-l
Fig. 3. Influence of tlzc extraction 1: Yicltl uf Ca(NO,)s, 11: Pruccnt Sr dissolved.
time.
Experiments were drawn in order to determine the influence of the extraction time on the yield and the purity of the Ca(NO,), obtained, using HNO,, d = 1.468. The results obtained for the less favourable ratio Ca : Sr = 20 mg : 80 mg are drawn in Fig. ;j. It is obvious that the best results are obtained when the extraction time is short. Extraction for 1.5 min is to be recommcndcd.
13nscd on the above cxpcrimcnts the following procedure has been izclopted: To a neutral mixture of calcium ant1 strontium nitratcs,a known amount of tracer Sr and Ce is added. After homogeneisation, HNO,, d =I 1.5 I, is adtlcd dropwisc under vigorous stirring until the final density rcachcs the value. tl = I .45, this taking about 30 to 40 zninlztcs. The Sr(NO,), precipitate is filtered off, The pure precipitate is filtered, washed with rcdissolvcd and purified by double precipitation. I-INO,, d = r.45, rlricd at 135~. and wcighcd as strontium nitrate. ‘fhc filtrate is evaporated to dryness. The residue is digested with IO ml PINO,, d = I .4(i8, for z 5 min and filtered. The filtrate, containing pure Clr(NO,), is evaporated to clryncss in ,thc prcsencc of an excess of sulfuric acid ant1 the resicluc is wcighcd as CaS?,. From the activities of a knowzz weight of each pure fraction, and of the pure tracer added, speczfzc activities can be computed azid the percentage of Sr and Ca can be calculated with the above forznula.
The procedure has been checked on a semi-micro scale with Ca-Sr mixtures I : I of total metal content of about 20 mg, weights being determined on the microbalance. Owing to the small weights of samples correction for self-absorption could be avoided when the measured weights of precipitate and of tracer were nearly equal. The results obtained by this method are shown in Table VII. It can be seen that the accuracy obtained with 20 mg samples is comparable that obtained by the best gravimetric methods with zoo mg samples. Referemes
.p. 320
with
16 (1957)
VOL.
__-_ - -....
DIS’CISRMINATIOS ._---.-.
Sulllple
__._
_.__ _ ___
.._
OIZ c:L .___... ___..
ST ,_____ ..__._ .._.__--.
I
.._
..-
BY Ttll: ISOTOPIC DILUTI0.V _._- -- .__-. -... _..w._ e-.-p
hIIST:101> ----.----.._-_
nrji /rmwl
_
_.___
.-.
II
ANU $I’ IN ~1IX’rUl~I~S _ .__. _ __.__._._. _- .__.._.. ..__
r,rg presolf
Cu _. __ _..__..
..-.-_-.
.SI
----.-
“/
__ ___ ._. _ . _ CC& sr --.-.-- ..--. -.-_I.___. ------.
.1Aif)
‘1.12
.5*(‘5
4 ~23
5.025
.1.18
5.145
4
83.1
.c*m,
_
. . .._._.
-I_ 3.2 --I. 2..1
CO _._._ . . _
+ 2.6 -1.3.6
‘I’llc cllli\l~tit;lti\~c sq):rr;tt.icJn of C’a xntl Sr by 511nlo of tllc IllIIst iritcrcsting cllcinical priJccIlIIrcs IL coliltl Lc sliown that nIJ satisIias I~ccri invcstifptccl, Iising rniliidicIiiic:~l tracer tcclinicliicn. fi~ctory scp~mtion ci~ul~l 1112 acliicvcd ;mtl ~:ooil rcslilts xrc olkiinctl in Some cilscs IJY compcnsi~tion of
errors.
‘I’lic rcnults Iii~vc: been Iiscil for tlw ilcvcliq~mc:nt ul :tli isotcq)ic ilililtion niutliotl for tllc rlctcrIniiiatic,n of <‘:L and Sr iii nlixtiircs uf tlicir SilltS. licli:L!h results we c~l~ttliiiotl on tlic scmi-microSCillC.
. IA
Si.lXtriLtic~ll
iIltJrcSSiLlltCS
nc
pcrtnct
ilii a
Gt.6
d’obtcnir
calcium
ct
i:tucli& Ilnc
illI
tlu llloycll
Sdparntion
l.cBslrMli
strontiiini 1xir ~1iii:lfliic!s-iilics ilcs liiStliotlcs J”(::l ct n”Sr. II S’cSt adr6 tics tribxllrs quWltitittiVc,
IlliliS
c\Il’~~ll olItic:nC
sou\‘cllt
cliiiniclucs C1ll’iLllCllllC! dcs
Its
plus
IIlIXlIotlc
l+dSUltiltS
satis-
f;iisniits pr compcnsik.tion tics crrciirs. 1.~4 rdsultrrts ant pcrmis tI’~tnl~lir iiilc nouvcllc in~tllotlc ])iLr cliliiticm isl>tcq>icluo pour In ddtcrS;ltiSfiliSnIlts Ollt dtc’ niination ties dcux LclJnicnts tlritis iin ni&lnii~c tic Icurs sols. IhS l+Slllti~tS 0lJtcIiIIs h l’~clicllc scmi-micro.
Eiiiigc tlcr gcbr!iucl~liclistcn clicniisclicn Mctlicxlcn znr ‘L’rcnnunK \‘on CillCilllll untl Strontium wurclcii wit I-lilfc tlcr Isotopcn 4nC;L iiiicl Wr rlntcrsclcht. Iis zcij+c sich tlass cinc cllli~lltit:lti~~e ‘h-cnniing nicnialu 211 crkliircn sind.
crfolgt
Iilitl giitc
~riLviriicLrisclic
I~CSllltiltC
vicllciclit
tlIlrclI
I~cllll~rl<~Jlllpcllsiltioll
IXc Ergcbnissc tlicscr 1~xpcrinwnt.c crlaubtcn tlic Ihtwicklun~ cincr luotoI,cllvcrtliinnrin~smcthorlc fiir clic Hcstinlrnung van Ca untl Sr in ihrcn Snlzgcn~isclwn. In1 Scminlikro-13crcich wiirdcn bcfriccligcriclc Resilltatc crhnltcll.