Re s
t’ u
v ?7b
e u 7
$I w
= = = = = = = = = = =
Reynoldsnumber speed of rotation, rev./sec. torque, ft. lb. velocity, ft./sec. viscosity, 1b.-sec./sq. ft. viscosity a t bubble point, 1b.sec./sq. ft. period, sec. specific weight, lb./cu. ft. shear, lb./sq. ft. angular displacement, radian angular velocity, radian/sec. LITERATURE CITED
(1) Bridgeman, 0. C., J . Am. Chem. SOC.
49, 1174 (1927). (2) Bridgman, P. W.,Proc. Am. Acad. A r t s Sci. 61, 57 (1926). (3) Chandrasekhar, S., Jfathematika 1, . i i l R54’i.
(4Ly Doolittle, A. K., J . A p p l . Phys. 22, \ - - - - I -
1031 (1951). (5) Floiwrs, A. E., h o c . A m . Soc. Testing Materials 14, 11, 565 (1914).
(6) Giller. E. 13.. Drickamer. H. G..
Kestin, J., “Dire the Viscosity of Gac and Tempeiatures,” TransFort Properties in Gases, pp. 62-74, Korthwestern University Press, Evanst’on, Ill., 1958. (9) Kestin, J., Pilarczyk, K., Trans. -4m. SOC.Mech. Engrs. 76, 987 (1954). (10) Kestin, J., Wang, H. E., J . A p p l . Mech. 24, 197 (1957). (11) Khalilov, K. J., J . Exptl. Theoret. Phys. (U.S.S.R.)9,335 (1939). (12) Landolt, H. H., Bornstein, R., “Physikalisch-chemische Tabellen,” 5th ed., p. 132, J. Springer, Berlin, 1923. (13) Meksyn, D., Proc. Roy. SOC.(London) A187, 115, 480, 492 (1946). (14) Pai, S.-I., “Viscous Flow Theory. Turbulent Flow,” T-an Nostrand, Princeton, X. J., 1957. (15) Reamer, H. H., Richter, G. N.$ I>e\T’itt, R. bf., Sagr, B. H., Trans. ; t t ? ~ .Soc. .l/ech. Engrs. 80, 1004 (195S!.
(16) Reamer, H. H., Sage, B. H., Reu. Sci. Instr. 24, 362 (1953). (17) Rossini, F. D., etal., “Selected Values of Physical and Thermodynamic Properties of Hydrocarbons and Related Compounds,” Carnegie Press, Pittsburgh, Pa., 1953. (18) Sage, B. H., Lacey, W. N., Trans. Am. Inst. Mining Met. Engrs. 127, 118 (1938). (19) Ibid., 136, 136 (1940). (20) Shepard, A. F., Henne, A. L., Midgley, T., Jr., J . Am. Chem. Soc. 53, 1948 (1931). (21) Steinman, H., Quart. A p p l . :Math. 14, 27 (1956). (22) Tausz, J., Staab, A., Petroleum Z. 26, 1129 (1930). (23) Taylor, G. I., Phil. Trans. Roy. Soc. London A223.298 11923). (24) Thorpe, T. E., Rodger, J. IT.. Ibid., A185, 397 (1895). (25) T’orlander, D., Fischrr, J., Rer. B65, 1756 (1932). RECEIVED for review Octolser 31, 1958. .\crepted 3Iarch 20, 1959.
Radiochemical Separations of Cadmium JAMES R. DeVOE and W. WAYNE MEINKE Department o f Chemistry, University of Michigan, Ann Arbor, Mich.
b Radiochemical separations of cadmium by solvent extraction with dithizone in basic media, by ion exchange in hydrochloric acid solution, and by two precipitation methods, one with an organic precipitant and the other with a complex inorganic precipitant, have been developed, allowing a maximum time of separation of 30 minutes per method. These methods have also been critically evaluated for yield and contamination using 18 typical tracers.
T
work continues a program of investigating radiochemical separations of various elements. The method of evaluation has followed closely that of Sundernian and Meinke (11, I S ) . Use of separations of cadmium is increasing as a result of interest in the fast fission reaction. While cadmium is of rather low yield in the slow fission process, the yield increases significantly in the fast fission reaction. Cadmium is not easily separated, and most procedures involve time-consuming scavenges followed by sulfide precipitations (1, 6, 16). Because of this, standard analytical methods were studied with a view towards modifying them for use as a radiochemical separation step. A maximum time of separation for any given step was placed at 30 minutes, sufficiently faster than the decay of most of the cadmium nuclides of interest. Two precipitation methods, a n ion exchange and a n extracHIS
1428
ANALYTICAL CHEMISTRY
tion method of separation, were evaluated. Most of the organic reagents used in the gravimetric determination of cadmium suffer from a lack of specificity and selectivity. A rather selective reagent is 2-(o-hydroxyphengl) benzoxazole ( 7 , 15). This reagent was studied to determine its effectiveness in a radiochemical separation. Another selective precipitant for cadmium is Reinecke salt (ammonium reineckate), fL“,[Cr(;”\”3)2(CKS)4]. The reagent has been known for many years but only recently has it been used (8) n-ith thiourea as a precipitant for cadmium. In view of its ability to separate cadmium from zinc, this precipitant was also evaluated. Yery fen radicchemical separations for cadmiuni have used solvent extraction techniqucs. Honfever, a large number of quantlttitive analytical niethods separate cadmium b j solvent extraction, with subsequent colorimetric determination of trace quantities or gravinietric determination of seniimicro quantities. Saltzman reports (9) that dithizone (diphen3-lthiocarbazoiie) extraction gives sufficient purity of cadmium for spectroscopic use, while Sandell (IO) has discussed in detail the use of dithizone in the analysis of rocks. The application of this extractant to high specific activity tracer solutions was studied in detail. Kraus and Kelson (4)have indicated that cadmium can be separated from
many elements by anion exchange. This procedure was also evaluated with high specific activity tracers. APPARATUS,
REAGENTS, AND PROCEDURES
Apparatus. T h e apparatus is identical with t h a t described by Sunderinan and Meinke (12, I S ) , n i t h the exception of a glow transEer scaler, N o d r l 162A, made b y the Atomic Instrument Co., Cambridge, Mass. Use of this instrument with the scintillation n-ell counter made it possible t o count up to 1,000,000 counts pcr minute n i t h less than 0.5% “coincidence” error in a 1-minute count. Reagents. Ammonium reineckate, SHI[Ci(KH3)2(SC?S)4]HzO, Eastman Iiodak reagent No. 3806. Solution, 4 grams per 100 ml. of 11-ater. Anion exchange resin AG2-X8, 200-100 mesh, Bio-Rad Laboratories, Berkeley, Calif., stored in 6 M hydrochloric acid until used. Chloroform, commercial grade unpurified. Dithizone (diphenylthiocarbazone), Eastman Kodak reagent KO. 3092. Stock soIution, 750.0 mg. per 100 ml. of chloroform. Working solution, diluted with chloroform to 0.75 mg. per nil. Hydrion p H paper (12 to 13.5). 2-(o-Hydroxyphenyl) benzoxazole, CI3H9O2?;, molecular weight 21 1.21 (HPBZ), Eastman Kodak reagent 6754, 0.1 gram in 135 ml. of 95% commercial grade ethyl alcohol. Thiourea, CSK2H4, Merck U.S.P. Solution, 5 grams per 100 ml. of water. A11 other nonradioactive chemicals
nere of analyzed reagent grade. The preparation of most of the carrier solutions has been described (Table I, I S ) . All additional carriers used here (cadmium, zinc, mercury, thallium, indium) were made by dissolving their nitrates in ~ a t e to r give 10 mg. of the element per ml. as Cd++, Zn++, Hg++, Ti+, and In tT, respectively. Many of the tracers have been described (Table 11, I S ) . Additional tracers used in this work are listed in Table I. Dithizone Extraction Procedure. Place 1 nil. of 20y0 sodium tartrate solution in t h e extraction vessel, add cadmium tracer for yield measurements or t h e contaminating element (11ithout carriers), and dilute m-ith distilled nater. Adjust the p H t o 13 to 13.5 n i t h dilute sodium hydroxide, using Hydrion p H paper. Total volume should be 10 ml. Add 10 ml. of dithizone solution and stir for 2 minutes. l h v off the chloroform layer into elactly 10 ml. of 0.1M hydrochloric acid. Stir for 2 minutes, and count aliquot of acid layer in well counter. Total time of separation is 10 minutes. Anion Exchange Procedure. Equilibrate t h e anion exchange column with 3.V hydrochloric acid. Pass tracers of the cadmium for yield measurements or t h e contaminating ion (without carrier) in 10 ml. of 3X hydrochloric acid through the column. Wash n i t h 10 nil. of 3M hydrochloric acid. Elute n ith 0.1M ammonium hydroxide, Discard the first 0.5 ml. and collect the next 3 ml. of eluent. Total time of separation is 15 minutes. Reinecke Salt Precipitation. Add 10 nig. of carrier and tracer of t h e contaminating ion t o a 15-ml. centrifuge tone and take t h e necessary steps to secure exchange. Add 10 mg. of cadmium carrier (as well as cadmium tracer n hen determining yield) and 2 mi. of thiourea solution (see discussion). Add 5 ml. of 2111 hydrochloric acid and dilute to 10 ml. Stir and add 2.5 ml. of Reinecke salt solution (see Discussion). Stir for 5 minutes, centrifuge for 5 minutes. and remove supernate by a suction tube ( 2 1 ) . Wash the precipitate by adding 10 inl. of 1% thiourea solution In 1 S Iiydrochloric acid and stirring for 5 minutes. Centrifuge and remove the supernate as before. Slurry the precipitate into a tube for counting in the well counter. Total time of separation is 30 minutes. 2 - (0 - Hydroxypheny1)benzoxazole (HPBZ) Precipitation. Add 10 mg. of carrier a n d tracer of t h e contaminating ion t o a 40-ml. centrifuge cone and txhe the necessary steps to secure exchange. ildd 10 mg. of cadmium carrier (plus tracer when determining cadmium yield). Add 3 grams of solid ammonium tartrate and heat to 60' C. Dilute with 20 ml. of distilled n ater and adjust pH to 13 =t 0.5 with Hydrion paper, using sodium hydroxide. Heat again to 60" and recheck pH. Slonly add 5.5 ml. of HPBZ and stir for 5 minutes at 60' C. Centrifuge for 5 minutes and remove the supernate by suction. Dissolve the precipitate in +
hydrochloric acid, measure aliquot into a counting tube, and count in well counter. Total time of separation is 28 minutes. DISCUSSION AND RESULTS
Yields for cadmium and contaminations for a large number of tracer impurities for the four procedures are listed in Table 11. KOcarriers were added for the solvent extraction and anion exTable I.
change procedures; 10-mg. amounts of cadmium and contaniinants were present for the precipitation steps. Because in some procedures the decontamination obtained may vary with the amount of element present, the TI eights of inactive elements used in these tests have been recorded in Table I1 for the two procedures tested without added carrier. The 43-day cadmium-l15m was used in these experiments. Although only about 2% of this isotope decays by
Chemical Characteristics of Tracer Solutions"
Isotope 1. Au198
For CarrierTracer Exchange
Source Au metal irrad. in hLichigan reactor 2 . Bi21O Atomic Energy of Canada, Ltd.c 3. Cd11Sm ORNLd; CdC1, in HC1 4. Cu6' C U ( K O ~irrad. ) ~ in Michiam reactor 5. Hg203 ORKLd~Hg(X03)2 in HNOi ORNLd; Iiic13 in HC1 OR?;Ld; IrCle--in HC1
Final Solution 0.5M HC1, 1.5.11 H?;O3 O.lLVHSO,
8. Xi@
0.1M "03
Xi( I1j
0.05211 HC1
Pd(1II)
9.
io.
Pd109 ~ 1 2 0 4
Xi metal irrad. in Michigan reactor Pd metal irrad. in Michigan reactor ORNLd;TlSO3 i n HNOq
b
Used as Au(II1)
b
Bi(II1)
I M HC1 Thorough mixing Cu(YO& in H20 b
Cd(I1) Cu(I1)
3U H K 0 3
Thorough mixing
Hg(I1)
0.5A1 HC1 0.2M HC1
Thorough mixing I r oxidized with Cl,, reduced with KH?OH.-
Ir(II1)
HC1
1M H?;Oa
11. ZnG
T1 carrier plus tracer. reduced with SaHS03e Thorough mixing
In(II1)
TU)
Zn(I1j ORSLd; ZnCL in HC1 1211 HC1 This t,able supplements Table TI of ( I S ) . K o additional-carrier used. Bi21Ois a decay product of Pb210,obtained as 1 mc. per 0 . 2 5 pound of I'b[XO&. Bizlo was separated by extraction of water solution of Pb(X03)2 at pH 2 . 5 into 0.5M thenoyltrifluorcacetone (TTA) in benzene, and back-extracted into 0.131 HX03. Isotopes Control Department, Oak Ridge Nat,ional Laboratory. e Exesss of reducing agent must be present to assure that T1 remains in +1 state. Table 11.
Contamination of Cadmium Separations"
I'recipitatior,, 5;
Added)c _ _(Carrier ___ ~___
Extraction, 5; ( N o Carrier Added)*
I011
Exchange,
s,
2 4 o-Hydroxy-
Reinecke salt 78f15
phenyl) beiizoxazole
i i f 1 . 7 ( 7 1) 80 =t 1 . 6 ( 7 y) 80zk18 ( 0 . 2 mg.) 89 (0 2 mg.) 99 4 i.4 (0.5mg.) , , , , . . . , . 0.1 (C.F.) 0.03 (C.F.) 0.06 . . 0.01 (C.F.) ... ... ... 0.02 (5.6r) 0.01 ( 3 ?-,I 0.03 5 0.03 ( : 3 . i 7) 0,007 ( 3 . ( -/) 0.05 80 0.1 (0.7 y i 0.02 (0 $;I 0.2 4 0.08 (0 3 -,j 0.007 ( 0 . 3 - 0 0.8 11 13 ( 4 mg.1 ... ... ... 0.1 (26 y) 36 (2G y ) 46 ... 0.06 (C.F.) 0.1 (C.F.) 0 ; 10 0.5 ( 0 . 1 mg.) 0.3 (16-,) 0.1 . . . 0.1 (0 0037) 0.015 (0.003 y) 0.08 9 0.09 (1: mg.) , . . ... ... 0.1 (1amg.l . . , ... ... 0.03 (2 y) 0.12 (1 y) 0 28 80 0.2 (0.6~) 4.6 (O.G.,) 3 11 0.01 (3.5y ) 0.01 (1.5r) 93 6 0.3 ( 0 . 2 mg.) 0.3 ( 0 . 2 mg.) 0.83 5 0.6 (5r) 0.005 ( 5 7 ) 0.06 10 91 (0 12 mg.) 0.007 (0.4mg.) 99 4 64 (36 Y ) 81 (90 Y) 0.6 8 0.1 ( 2 y) 0.03 ( 2 y) 0.04 ... 0 Average of duplicate runs except for cadmium, which is average of quatlruplicate runs. Errors are "standard deviations." b Keight of inactive element prior to separation indicated in parentheses. c 10 mg. Cd, 10 mg. contaminant carrier added. ~
~ ~ _ _ _ _ _ _ _ _ _ _ _
VOL. 31, NO. 8, AUGUST 1959
1429
Table 111.
Yield D a t a for Precipitation Reactions of Cadmium
[hmmonium reineckate = R; 2-(o-hydroxyphenyl) henzosazole = HPBZ] yo %n Carried with Cd Tieltl Precipitating Condition Cd P p t . (Est.), 5% Solution 1 50 1.75 nil. of 4% solution of R ; pH 4 (HCI) 1% thiourea pH 3 (HC1) 0.9 50 0.8 50 pH 2 (HCI) pH 0 (HC1) 0.6 50 1.75 ml. R 0.9 50 4% solution of R a t pH 3; 1% thiourea 2 . 5 ml. R 0.8 80 6 27cthiourea 2s 70 2.5 ml. of 47, solution of R ; 2 (yothiourea 1.8 70 PH 3 1 0% thiourea 1 4 70 0 8% thiourea 1.7 70 1 5 70 2.5 ml. of 4yo solution of R ; O-wsh(lyo thiourea) 1 wash (1% thiourea) 02 ti0 pH 3; 1% thiourea 2 wash (1% thiourea) 0.04 60 80 90 5.5 ml. of 1% HPBZ; 10% $1; 60 90 (SH,),C?O, pH 12 8 no pH 13 8 DO 5 g. (NH4)zCz04/100 ml. 19 5.5 ml. of 1% HPRZ; pH 13 10 g. (~H,)zCz04/100 ml. 11 15 g. (NH4)zC204/100 ml. 8 5 5 ml. HPBZ 1% HPBZ;pH 1 3 >157) 8 4 (SHdzCzOh 4 Oml. HPBZ 2 5 ml. HPBZ 2 5.5ml.of l % H P B Z ; p H 13; O\vash(amnioniacalethyl 8 15% (NH,)GO* alcohol) 1 wash (ammoniacal ethvl 4 alcohol) 5 wash (ammoniacal ethyl 4 90 alcohol) Table IV.
Typical Radiochemical Determination of Cadmium
Cd, B g , Ba, Ce, Co, Cr, Cs, Hg, I, I n , 11..Ru, SI),Sc, 311,T:L> TI, %n. %r 1. -Idd 1 ml. tartrate solution 2 . Adjust pH t o 13 with NaOH. Total volume 10 ml.
3. Add equal volume dithizone in CHC1,: stir for 2 minutes 4. Re-extract with equal volume 0.131 HC1; stir for 2 minutes
103-104Cy, CO. C., I.
Dithizone extracri ~ i of i cailmium
Itii
''P
Yirtld 7 T f ' i
5. Add concd. HCI until solution 3M HC1 6. Pour through Doffex I1 column; wash with 10 ml. 3M HC1 7. Elute with 0.1M KHaOH; discard f i i c t 0.5 ml. Collect next 3 ml.
8. Add 10 mg. of carriers of Cd and con-
9.
10. 11.
12. 13.
taminatinr ions .kdd 0.1 g.-of thiourea i n solution. Also add HC1 and dilute t o make 10 ml. of 1111 HCI Add Reinecke salt solution. Stir 101 5 minutes Centrifuge for 5 minutes; remove supernate Wash ppt. with 10 ml. lyOthiourea i n 1M HC1. Stir for 5 minutes Centrifuge and remove supernate
I Reineckate precipitatitJn of c.:rtlmiiim 1
Yiclltl -4gr
14. Mount precipitate for counting with Geiqer tube or dissolve iu hot 3.M HCI anil count in scintillation well counter 1430
ANALYTICAL CHEMISTRY
g:imma emission, the bremsstrahlung froin the 1.61-m.e.v. ,+particle constituting most of the decay is sufficient so that this isotope can be measured easily in the scintillation well counter. Extraction. Dithizone is known to react wit'h a great many of the heavy metal$, but cadmium is almost unique in bciiig able to form a stable dithizonatc in strongly basic solution. Charlot and Ikzier ( 2 ) have included a graph of per cent extraction us. pH for most of the heavy metals which form dithizonates. The separation procedure outlined above has evolved from this information and experiments in the laboratory. Of the 23 elements listed in Table I1 only silver, copper, thallium, and zinc contaminate the separation. The presence of 1M ammonium hydroxide in the original solution satisfactorily complexes the silver, preventing Contamination, but contamination by the other thrce elements is not affected. When the basicit'y is increased to 0.5M sodium hydroxide, t'he copper contamination is reduced to about O.lyo. The increased l m i c strength often reduces the strength of the dithizonate bond. This is probd)ly caused by increased solubility of the clit'liizone in the basic aqueous layer, thereby displacing the equilibrium toward dissociation of the dithizonate. Unfortunately, the yield of cadmium is also rcduced to about 50% by this step. The contamination of thallium can l ~ c conveniently removed by utilizing a displacment reaction (9). An equal volume of a solution made up with 0.1 grain of cobalt nit'rate, 5.0 grams of sodium acid tartratc, and 4.0 grams of sodium acid carbonate in 1 liter of water is agitated n-ith a chloroform solution of thc cadmium and t'hallous dithizonate. The cobalt displaces the thallium to form the dithizonate, but the cobalt will not displace cadmium. This procedure, therefore, renim-cs the contamination with inactive cobalt'. Subsequent removal of the cadmium in 0.1111 hydrochloric acid removes cadmium but very littlc inactive cobalt. The decontamination factor obtained from thallium by this iiiethod is 0.S570, with a cadmium yield of 65%. Unfortunately, this displaceinent did uot occur with zinc. In many cases the radiochemist is interested only in a pure activity. The presence of even large amounts of in:ictive foreign ions is unimportant. Therefore, this method of selectivc displacement of a persistently contaminating ion should be of use in many radiochemical separations by solvent extraction. Ion Exchange. Because cadmium forms very slightly dissociated rhloridt c'oniplexes, t h e anion exchange sep:tmt,ion was of interest. Kraus and Srlsoii (.i)have reviewed this rnet'lioti. and Hicks and coworkers (39 spc'cifically tried Dowex I1 resin with a
\vide variety of elements in a hydrochloric acid medium. The cadmium chloride complex will be held very strongly, while many metals xhich do not form complexes can be u-ashed through the column with dilute hydrochloric acid. Experimental contamination u l u e s for IS tracers are listed in Table 11. As \\ ould be expected, all cations that form m e n moderately undissociated complexes with chloride ion remain on thc column at high chloride ion concentration. The high acid concentration was used to prevent hydrolysis of cations hich would then adsorb on the column :ind elute over a wide volume of eluent. causing contamination. Special care must be taken to ensure that thallium i* all present in the +1 state. This is :ircomplished by heating the solution n i t h 0.1M sodium bisulfite. Ion exchange can be used to separate zinc, mercury, and silver from cadmiurn hy using distilled water instead of aniinonium hydroxide as eluent. I n this case the water acts as a true chromatographic eluent. The impurities elute in the first 6 free volumes, while the cadinium does not elute until 9 free volumes Iiave been collected. I n this modified procedure the yield of cadmium was tound to be about 55%, with a eontarnillation of 1.0, 0.5, and 0.3% for zinc, mercury, and silver, respectively. Reinecke Salt Precipitation. The itructure of t h e rcineckate anion is
The contamination data for 19 elements are listed in Table 11. Silver and thallium undoubtedly precipitate as the chlorides. The use of nitric acid for these elements does not, however, improve the separation because they, with mercury, also form insoluble reineckates. Selenium is reduced b y thiourea to the metallic state. Removal of thiourea will lon er the contamination of selenium, b u t the over-all contamination may increase because of the loss of crystallinity in the precipitate. With thiourea the cadmium precipitate is rose in color and is very granular and crystalline, a fact which substantiates the postulated ionic structure. Ammonium reineckate, when dissolved in distilled water, slowly decomposes on standing to give the greenish blue chromium-ammonium complex. Thus a solution of the ammonium reineckate ( 5 ml. of 4 grams per 100 ml.) was unable to precipitate 10 mg. of cadmium in 5 ml. of water 72 hours after preparation. The precipitation was quantitative, however, if the reagent was used during the first 24 hours after preparation and if a 10% excess of reagent was used. HPBZ Precipitation. Cadniiuni presumably forms a complex similar to the structure below:
(I.$):
YH3
I
S=C=X--N=C=S
kH3 N o s t commonly the cadmium ion is complexed with thiourea (increasing the size of the cation) before the reineckate is precipitated. Cadmium, as well as mercury and copper, has been successfully precipitated without the thiourea, hut a distinct advantage is derived by the complexation. -1 suitable colorimetric method has been used by X a h r ( 5 ) for these three elements using Reinecke salt. The manner in which the cadmium-dithiourea complex cation is chemically bound to the reineckate anion is believed to be closely related to the ionic type of bond (8). The effects of variation of the concentiation of the thiourea, pH, amount of Reinecke salt added, and number of \\ ashes of the precipitate for the separation of cadmium from zinc is shown in Table 111. The addition of too much thiourea (6.9%) evidently results in the formation of a complex with zinc and i t vontaminates the separation by forming :i precipitate with the reineckate anion.
Cadmium will not be precipitated by HPBZ a t a pH less than 2 nor in a concentration of base of greater than 1 . O M sodium hydroxide. To use this precipitant the easily hydrolyzable metals were complesed with ammonium tartrate. The separation of cadmium from zinc was used to measure the systematic variation of the pH, amount of HPBZ, concentration of ammonium tartrate, temperature of the precipitation, and time of stirring on the efficiency of separation (Table 111). The large decrease in contamination above p H 10 is probably due t o the increasing amount of tartrate anion formed with increasing pH. As seen from Table 11, there is considerable contamination for all elements. W i t h the exception of cobalt and ruthenium, the contamination is probably due to occlusion and surface adsorption. This is indicated by the fact that washing the precipitate with ammoniacal 50% ethyl alcohol reduced the contamination of zinc from 8 to 4%, but continued washing of the same pre-
cipitate did not further reduce this value. Heating the precipitatc a t 60” C. for 5 minutes reduces the gelatinous nature of the precipitate and facilitates centrifugation.
SUMMARY
The best separation from the standpoint of contamination, elements that can be separated, and time of separation (10 minutes) proved to be eutraction n i t h dithizone in chloroform. Elements that did contaminate the extraction include silver, thallium, copper, and zinc, although supplementary procedures ran improve the separation from copper and thallium. Contamination values for ioii PYchange were low for most elements. tlrspite the nonequilibrium conditions imposed when the time of separation is limited. Although mercur?., silrrr. zinc, and antimony contaminate, this contamination for all but antimony could be reduced by a further selective elution. Precipitation with Rrinrcke salt resulted in good decontamination e w c p t for silver, mercury, selenium, and thallium. Z-(o-Hydroxyphenyl) benzoaaznlc formed a bulky precipitate a hich ~ n trained 5 to 10% of most elements. \\ 1-111~ mercury and cobalt contaminated to thc extent of 80%. Combination of these separation steps can provide a procedure to suit many types of samples. Table I Y s h n w the over-all decontamination fartors a n d cumulative yields n-liich could be obtained if the extraction, ion exchangt,, and Reinecke salt precipitation separations were conducted in that order. (Decontamination factor here nieans the ratio of activity prior to separation to activity after separation.) The least separation is that from silver. Eatraction is the only one of the three procedures which gains any separation from silver, so that a single repetition of this separation step could give a decontamination factor of lo4. The same applies to the Reinecke salt separatioll from zinc. LITERATURE CITED
(1) Beaufait, L. J., Jr., Lukens, H. R.,
Jr., U. S. Atomic Energy Comm., Ilept. NP-5057(May 1953). ( 2 ) Charlot, G., Bezier, D., “Quantitative Inorganic Analysis,” Wiley, New York, 1955. (3) Hicks, H. G., Gilbert, R . S , Stevenson, P. C., Hutchin, W. H., U. S. Atomic Energy Comm., Rept. LRL-65 (December 1953). (4).Kraus, K. A., Kelson, F., International Conference on Peacetime Cses of Atomic Energy, Geneva Paper 837 (1955). ( 5 ) Mahr, C., 2. a n d . Chon. 104, 241 (1936). (6) Meinke, IT.IT.,C. S. Atomic Energy VOL. 31, NO. 8, AUGUST 1959
1431
Comm., Rept. AECD-2738,138 (August
(15) Walter, J. L., Freiser, H., ANAL. CHEM.24, 984-6 (195"). (16) Wilkinson, G., Grummitt, W. E., Nucleonics 9 (KO. 3), 52-62 (1951).
1949). (7) Nordling, W. D., Chemist Analyst 45, 44-5 (1956). (8) Rulfs, C. L., Przbylowicz, E. P.,
RECEIVED for review- February 12, 1959. Accepted June 19, 1959. Division of Analvtical Chemistrv. 134th Meetinn. ACS; Chicago, Ill.," ' September 195i: Work supported in part by the U. S. Atomic Energy Commission.
Skinner, C. E., ANAL.CHEM.26, 408 (1954). (9) Salteman, B. E., Ibid., 25,493 (1953). (10) Sandell, E. B., IND.ENG.CHEM., ANAL.ED. 11, 364 (1934).
Melting Point Apparatus for Simultant,,, of Samples in Transmitted and Reflecl H. E. UNGNADE, E. A. IGEL, and 6. B. BRIXNER University of Cofifornia, 10s Afamos Scientific Laboratory, Los mIuIIIyJ,
b A melting point apparatus utilizes an electrically heated copper block and an optical system which projects both transmitted and reflected images of the sample side b y side on a rear projection screen. It is particularly suitable for use with explosive materiols.
T . .
HE copper block . apparatus for determining capillary melting points has been used extensively since its introduction in 1927 ( I ) . Various suggestions have been made for optical systems t o facilitate observation of the sample (3-4). The use of light sources, lenses, screens, etc., has made it possible to observe enlarged images of the sample either in transmitted or in reflected light. It is often desirable, however, to observe both transmitted and reflected images simultaneously for a complete study of the phase transition during or prior t o melting. The apparatus described below was constructed for this purpose.
Figure 1.
Melting point appc
Copper block pulled out and resting on 3plit-ring top of lamp housing removed
1432
-
ANALYTICAL CHEMISTRY
,",
APPAR L
U
~ucw
ULUULL~
pumb apparaiuv
shown in Figure 1 consists of a n electrically heated copper block insulated by a Transite housing, a 200-watt light source, and an optical system which permits the 1OX enlarged images of the melting point tubes to be viewed on a 5 X 6 inch screen with normal room illumination. It is portable and self-contained. All power units for heating and lighting, as well as their controls, are found in and on a single aluminum housing. The melting point block is a stepped copper cylinder, 3 inches long by 2'/$ inches in diameter, which has a '/rinch long indexing flange. The periphery of this flange contains a '/16-inch wide X %&nch deep slot into which fits a '/,Anch diameter index nin t o alien
mis nange, m e diameter of the block is 2l/4 inches for a length of 23/, inches. A 3/r-inch diameter hole (the optical cavity) was drilled through the block, perpendicular to the axis of the cylinder and 3 / n inch from the bottom-i.e., the end away from the index flange. The optical cavity is sealed by I-mm. thick quartz windom, locked into position by snap rings. On the axis a t the bottom of the block there is a 24 hole tapped through t o the optical cavity. A 3/s-24 bolt is fitted into the tapped hole and affords a n adjustable base or platform on which the melting point tubes rest. Two '/&ch diameter X Z8/,inch long holes were drilled from the bottom of the block to accommodate two stainless steelsheathed Chromalox heaters (Edwin I,. Wieemtl C n ) ~Cnt.nlnp No m2-c
