Table I11 summarizes the analysis of several standard solder samples. Utilizing the procedure suggested, a series of 44 samples, presumably 37.5% lead, 37.5% tin, and 25.070 indium were analyzed; the results were 37.2 0.7% lead, 37.8 0.4% tin and 25.2 + 0.2% indium. Several other lead-tin solders, where the lead content varied from 40 to 60%, gave similar results.
*
*
ACKNOWLEDGMENT
Appreciation is extended to Joseph
0. Frye, this laboratory, for preparation of standard solders used in this investigation, LITERATURE CITED
(1) Elving, P. J., Van Atta, R. E., ANAL. CHEM.26, 295 (1954).
(2) Kolthoff, I. M., Johnson, R. A., Zbid., 23, 574 (1951). (3) Miura, Y., Bunseki Kagaku 7, 779
(1958).
D.E.SELLERS I).J. ROTH
Mound Laboratory hlonsanto Research Corp. hliamisburg, Ohio Mound Laboratory is operated by blonsanto Research Corp. for the U. S. Atomic Energy Commission under Contract No. AT-33-1-GEN-53.
Separation of Alkaline Earth Elements by Anion Exchange SIR: Ion exchange has been used for the separation of the alkaline earths by other methods (2-5). The results obtained by the authors in the investigation of the anion exchange equilibria of alkaline earths in the presence of 2,6pyridinedicarbosylic acid suggested that this system might prove convenient for the separation of these elements (1). It would also be of interest to observe the correlation between batch equilibrium studies and the elution behavior. I n the previous study (1) the distribution coefficients, defined as
I
0.00 I
=
K D
were measured as a function of the concentration of ammonium 2,6pyridinedicarboxylate (Figure 1). At high concentrations of complexing agent all of the distribution coefficients are low. At low concentrations of complexing agent, strontium and calcium have large distribution coefficients, while those of magnesium and barium are low. This suggests that this system should allow the separation of calcium or strontium from magnesium or barium. EXPERIMENTAL
The ion exchange resin used was Dowex 1, 50-100 mesh with 8% crosslinkage. This form was used since it was the same as the form used in the distribution studies. The elution experiments were performed using a resin column 37.6 cm. long in a glass tube of 5.2-mm. diameter. The density of the
Table I.
Experiment 2b
a
b
Element hk Ca Ba
2b Sr Eluent change at 75.5 mi. Eluent change at 56.0 ml.
51 8
0.01
.
, , , ,\
I 0.I
I
LIGAND M O L A R I T Y
Moles of metal ion per kg. of dry resin Moles of metal ion per liter of solution
15 1‘
. . . . . . .. I
ANALYTICAL CHEMISTRY
Figure 1 . Plot of the log of the distribution coefficient of metal ions as a function of the log of the molarity of 2,6-pyridinedicarboxylic acid
column was 0.492 gram per ml. and the fractional interstitial volume was 0.53. The resin was used in the 2,6-pyridinedicarboxylate form. The metals were added to the column by placing 0.2-ml. aliquots of 0.25df solutions of the metal chlorides on top of the resin column. Elution was carried out with the appropriate concentration of ammonium 2,6-pyridinedicarboxylate a t a rate of approximately 0.5 ml. per minute. The pH values of the eluting solutions ranged from about 7.1 for the most dilute to 7.6 for the most concentrated. The titration data ( I ) indicate that the distribution coefficient between pH 7 and 10 is constant. Above a p H of 10, hydroxide ion might compete for resin sites; below a p H of 7, hydrogen ion will compete for the ligand. The elution was monitored in most cases by a conductance cell a t the bottom of the column. The conductance cell was one arm of a conductance
Quantitative Data on Separations
Taken, mmole 0.100 0.050 0.050 0.050
Found, mmole 0.103 0.050 0.050 0.047
Eluent vol. range 0 to 75.5ml. 78.7 to 100.5 ml. 0 to 56.0 ml. 61.0 to 96.6
bridge, the off-balance of which was plotted on a recorder. Effluent samples were analyzed by flame photometry. The samples were ignited in platinum crucibles. The metal oxide was dissolved in 3.ON HC1 and again evaporated to dryness. The metal chloride residue was then dissolved and analyzed for metal content by flame photometry. ; iBeckman DU, with the flame photometer attachment, was used. The reagents were prepared and analyzed as given previously (1). RESULTS A N D DISCUSSION
I n one experiment a misture of magnesium chloride and calcium chloride was placed on the top of the column and then the magnesium was removed with 2.0 x 10-3.11 ammonium 2,6 - pyridinedicarboxylate (Figure 2). The calcium remained on the column. Then, a 1.0 x 10-1M eluent was used and the calcium was removed (Figure 2 ) . This complete separation can be explained on the basis of the distribution coefficient difference for magnesium and f calcium a t 2.0 x 1 0 - ~ ~complexing agent. A similar experiment was carried out using a mixture of barium and strontium (Figure 3). The same complete separation was obtained. A quantitative representation of the
0.002 M LIGAND
+ 0.100 M LIGAND
.0.002M LIGAND
0.010
COLUMN VOLUMES
COLUMN VOLUMES
Figure 2. Elution separation of magnesium(l1) and ca Icium( II)
results was determined (Table I) by the summation of the individual aliquot analyses for each element. Similarly, one can predict t h a t the same technique would work for calciumbarium mixtures and strontiummagnesium mixtures. The same would hold true for the removal of magnesium or barium from a mixture of that element with calcium and strontium, and the removal of calcium or strontium from a mixture of that element with magnesium and barium.
r' 0.100 M LIGAND
Figure 3. tium(l1)
Elution separation of barium(l1) and stron-
This system provides a convenient method of separation requiring few reagents. The strong retention of magnesium and strontium at low eluent concentration should allow their separation from fairly large excesses of the other elements. LITERATURE CITED
Bennett, William E., Skovlin, Dean O., in press. (2) Fritz, James S., Waki, Hirohiko, Garralda, Barbara B., ANAL. CHEM. 36, 900 (1964). (1)
(3) Davis, P. S., Nature 183,674 (1959). (4) Nelson, F., Krause, K. rl., J . Am. Chem. SOC.77,SO! (1955). (5) Tsubota, H., Kitano, Y., Bull. Chem. SOC.Japan 33, 770 (1960). WILLIAME. BENNETT DEAN0. SKOVLIN Department of Chemistry University of Iowa Iowa City, Iowa INVESTIGATION supported in part by Research Grant RG-5532 from the Division of General Medical Sciences, Public Health Service.
Determination of Sodium, Arsenic, Copper, and Gallium in Tin Oxide by Neutron Activation SIR: Many elements and matrices have been esamined by nuclear activation, and the technique is now well eitabliqhed ( 2 , 3). Little work has been done, however, on the activation determination of impurities in tin or its compounds. The author is aware of only one published reference, a survey aiticle where mention is made that antimony was determined in tin in the 35-50 p.p.m. range (6). Tin has ten stable iqotopes, more than any other element, and interfering activities induced by (n,y) reactions in tin cover a wide range of half lives and radiations (10). We report here the details of come activation work in tin oxide, where chemical separations were used to handle the interferences, in order to deinonqtrate that tin matrices can be treated with reasonable ease. The mate1 ial analyzed was high-purity calc3ined nietastannic acid, used for the giowth of tin ohide single crystals (?'), and the baqic approach was to compare the amount of impurity activities isolated from an irradiated sample with those from standards, corrected for ]owes by chemical yield determinations.
EXPERIMENTAL
Irradiations were carried out in the Swimming Pool Reactor a t Industrial Reactor Laboratories, Plainsboro, N. J. Activated samples were fused with sodium peroxide, and subsequent purification procedures followed the radiochemical literature (1, 4 , 6, 8, 9). Sodium was separated by ion exchange using Dowex-1 (Cl-) , arsenic by sulfide precipitation, copper by thiocyanate precipitation, and gallium by ether extraction. Irradiated oxide standards for arsenic, copper, and gallium were purified as above, while sodium carbonate standards were counted directly. Chemical yields for samples and standards were measured for the arsenic, copper, and gallium procedures; the sodium procedure was quantitative. The radiochemical purity of the separated NaZ4,As76, C d 4 , and Ga72 was established by gamma-ray spectrometry and half-life determinations, while activities were assayed by routine beta or gamma counting. RESULTS AND DISCUSSION
The results of the determinations are shown in Table I. The average of four determinations is given in each case,
and the errors quoted are average deviations. Because wider precisions were obtained for some methods than for others, indications are that a systematic examination of procedural steps would lead to improved precision. Still the precisions obtained gave useful analytical information. Firm estimates as to accuracy could not be made, however, since alternate methods of analysis did not detect the above elements. The examples given here show that trace elements in tin matrices are certainly accessible by neutron activation. The many induced tin activities may hamper automated methods of spectrum analysis, but an approach using chemical separation of interferences seems quite feasible.
Table
I.
Trace Elements in Tin Oxide
Element Sodium Arsenic Copper Gallium
Parts per million 1.6
f 0.5
0.42 k 0.25 0.50 k 0.03 0.043 k 0.012
VOL. 38, NO. 3, MARCH 1966
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