ing this same magnitude of reproducibility to the carbon values, sections 4-5 to 8-9 are statistically identical (6 p.1i.m. +35%), whereas sections to either side of these show a significant increase in concentration. CONCLUSIONS
Since no particular difficulty in the determination of C, 0, and T S was posed by the widely different matrices (Fe, Mi, Cu, and rig) used in this study, it is concluded that the proposed method of analysis can be extended to metals of all types. Calibration for corrective sensitivity factors can be performed on available high p.p.m. samples with confident linear extrapolation to low concentrations of C, 0, and Tu’. With the materials available for this study no instrument blank level was apparent that would adversely affect linear extrapolation to concentrations of C , 0, and K in the p.p.b. range. Because other blank lowering procedures such as extensive baking are time consuming and apparently non-reproducible, the faster method of cryosorption pumping in the source chamber is especially valuable in lowering and controlling the level of C, 0, and Tu’, as well as hydrocarbon species. The time required for a determination of these elements using the cryosorption method
is no different from that for normal spark source procedures where presparking is employed. T h a t is, analysis of a metal for C, 0, and IT from sample preparation through data reduction would require about 3 hours. Dividing instrument operation and data processing between two people would increase the daily sample throughput by a factor of three. Although average bulk concentration values are useful in many applications, the degree of homogeneity or the impurity distribution is more important to most metallurgical problems. The scanning method presented here offers a guide to the degree of homogeneity, and the localized sampling of the rf spark is shown to produce an accurate, precise representation of impurity distribution. ACKNOWLEDGMENT
The authors thank Professor E. Scala, Materials Science and Engineering Department, Cornel1 University, for supplying the zone refined tungsten rod used in this study. LITERATURE CITED
(1) Albert, P., Proc. Znt. Conf.: Modern Trends in Activation Analysis, pp. 78-85, College Station, Texas, 1961. (2) Bate, L. C., Nucleonics 21, 72-5 (1963). (3) Fassel, V. A,, Dallmann, W. E.,
Skogerboe, R. K., Horrigan, V. M., ANAL.CHEM.34, 1364 (1962). (4) Gordon, W. A., Graab, J. W., Tumney, Z. T., Zhid., 36, 1396 (1964). (5) Goward, G. W., Zhid., 37, 117R (1965). (6) Harrington, W. L., Skogerboe, R. K., Morrison, G. H., Zbid., 37, 1480 (1965). (7) Henry, W. M., “Development of Anal. Tech. for the Uetn. of Minute Quantities of Selected Elements in Beryllium,” Battelle Memorial Institute Final Report, July 22, 1963. (8) Iron and Steel Institute Special Report, 68, “The Detn. of Gases in Metals,” London, 1960. (9) Kennicott, P. R., “A Computer Program for the Quantitative Interpretation of Mass Spec. Plates,” Report No. 64-=-3766G, Research Information Section, General Electric Research Laboratory, Schenectady, N . Y., 1964. (10) MFCrea, J. XI., “Developments in Applied Spectroscopy,” Vol. 4, E. N. Davis, Ed., p. 501, Plenum Press, N. Y., 1965; Spectrochim. Acta 21, 1014 (1965). (11) Roboz,,;J., in “Trace Anal.: Physical Methods, G. H. Morrison, Ed., p. 497, Interscience, New York, 196s; Proc. XI Ann. Conf. Mass Spectrometry and Allied Topics, Paper 103, San Francisco, 1963. (12) Socha, A. J., Willardson, R. K., XI Anntial Conf. on Mass Spectrometry and Allied Topics, Paper 84, San Francisco. 1963. (13) Winge,’ R. K., Fassel, V. A., ANAL. CHEM.37, 67 (1965). RECEIVEDfor review March 7, 1966. Accepted April 11, 1966. Research supported by the Advanced Research Projects Agency.
Quantitative Separation of Mercury-Thallium Mixtures R. G. DOSCH Sandia laboratory, Albuquerque, N.
M.
b Two methods for quantitative separation of Hg and TI are described: a cation exchange method using HCIO4 eluent with a separation time of 3 hours, and a reduction procedure using SO?to reduce Hg(l) and Hg(ll) to Hgo with a separation time of 15 minutes. Procedures were applied to mixtures ranging from Hg(ll)-TI(I) ratios of 20: 1 to TI(I)-Hg(II) ratios of 5:l.
I
in low temperature switch materials has initiated compatibility studies between Hg-TI amalgams and a number of different materials. Collection and reduction of data obtained from these studies require quantitative chemical analyses to determine initial and final compositions of the Hg-T1 amalgams used in the experiments. Several methods have been used to separate H g from T1 prior to analysis. NTEREST
826
ANALYTICAL CHEMISTRY
Foley and Osyany (2) used formic acid to reduce Hg(I1) from solution as Hg’, the thallium remaining in solution as Tl(1). The method of Richards and Daniels (8) involves bubbling air through the amalgam to form thallous oxide and free mercury, followed by selective dissolution of the oxide with dilute sulfuric acid. Korenman (5) suggests precipitation of thallium as T12Cr04 in ammoniacal media in the presence of KCN. The Hg(I1) ion forms a stable complex with KCN and does not react with KICrOI. Bhatnager and Trivedi (1) used sodium nitrite to elute Hg(I1) in a cation exchange separation of Hg(I1)Tl(1) mixtures. The Tl(1) was subsequently eluted with sodium sulfate solution. The purpose of this work was to find a rapid procedure to effect a quantitative chemical separation of mercury and thallium applicable t o the analysis of
Hg-TI amalgams. The previously described methods were considered to be undesirable for this purpose due to lengthy reduction and oxidation procedures, incomplete separation, or large eluent volumes. This paper describes two procedures for quantitatively separating Hg-TI mixtures: a cation exchange procedure using HC104 as the eluent and a reduction procedure using SO, to reduce Hg(1) or Hg(I1) to Hg”. Quantitative recovery of mercury and thallium was obtained in both procedures using mixtures ranging from Hg(I1)-Tl(1) ratios of 20: 1 to Tl(1)-Hg(I1) ratios of 5 : 1. I O N EXCHANGE SEPARATION OF MERCURYTHALLIUM MIXTURES
Experimental. COLUMN PREPARAT h e borosilicate glass ion exchange columns were 30 X 1 cm. (i-d.). The resin used was Dowex TION.
Table 1.
Analysis of Hg-TI Mixtures
TI, mg. Present Found" 10 4-
52
104
10.4
51.7 104
mg.
Present
Founda
21.1 105.6 211.3
20.9 105 210
Each number represent? the average of three determination, obtained by taking the given listed amount of TI or Hg and varying the Hg or T1 eoncentration to give solutions of approximate Hg:T1 ratio of 20:1, 1:1, 1:5. Q
Figure 1. Elution curves of thallium and mercury, 12.5% HCIOd, now rate 2 ml. per minute
dG-5OWX8, 100- t o 200-mesh, hydrogen form. Twenty-seven grams of resin, dry weight, were used in t h e columns. The resin was washed several times with distilled water, and the finest' particles were decanted after each washing. The resin then was washed with 1 N HC1, followed by distilled water washing until a negative chloride test was obtained. REAGENTS.Mercury and thallium standard solutions were prepared from triply distilled mercury and A. R. grade thallous nitrate, respectively. Solutions were standardized using standard analytical methods (3, 4). The 2.5% HCIOa eluent was prepared by dilution of A. R. grade iOYOHC104 to desired volume. A 91.75% Hg-9.25% T1 amalgam was obtained from Taylor Instrument Co., Tulsa, Okla., in a sealed container. T h e container was opened and stored in an argon atmosphere containing less than 1 p.p.m. O2 and less than 10 p.p.m.
Hz0. PROCEDURE. Samples of the amalgam were placed in quartz ampoules, evacuated, and sealed before removal from the argon atmosphere. To prevent error in sample weight due to air oxidation of the thallium in the amalgam, the ampoules were broken under distilled H20 after the weight of the ampoule plus amalgam was obtained. Dissolution of the amalgam in a mininium amount of HX03 was done by covering the amalgam with H20,heating to near boiling, and adding HNOl dropwise until the reaction was complete. The resulting solution was filtered to remove the quartz, the weight of which was subtracted from the weight of ampoule plus amalgam. A coldfinger was used during dissolution of the amalgam to prevent loss of mercury by volatilization. The Hg-T1 solutions obtained from the dissolution of amalgam and from standard solutions were diluted until the Hi\j03 concentration was less than 1% and were put on the column a t a flow rate of 2 ml. per minute. Both mercury and thallium were eluted with 12.5% HCIOI at a flow rate of 2 ml. per minute. Elution curves for mercury and thallium, Figure 1, were determined by
standard techniques. Ten-milliliter fractions were collected and the mercury and thallium were analyzed polarographically using a Davis Differential Cathode Ray Polarograph, Model A 1660, obtained from Southern ilnalytical, Ltd., England. With the exception of elution curve data, all mercury analyses were done volumetrically by a complexometric titration with thiocyanate (4). All thallium analyses were done polarographically. Results and Discussion. Figure 1 is a n elution curve for a solution containing 50 mg. of Ti(1) and 100 mg. of Hg(I1). T h e solution containing less t h a n 1% H N 0 3 was p u t on t h e column and eluted with 12.5% HClOI a t tt flow rate of 2 ml. per minute. Failure to keep t h e "03 concentration below 1% when putting t h e Hg(I1)Tl(1) solutions on t h e resin causes t h e subsequent elution of Tl(1) to tail badly, and Tl(1) elution is not complete before Hg(I1) appears in the eluent. An attempt was made to determine the cause of thallium tailing when put on the resin in greater than 1% "03 solutions. I n discussing the behavior of Tl(1) on cation exchange resin, Bhatnagar and Trivedi ( 1 ) state t h a t thallium put on a cation column as Tl(1) is eluted as Tl(II1) by 5% "03 solution. Attempts to reproduce their observation in this laboratory proved unsuccessful as no evidence of oxidation of Tl(1) to Tl(II1) by 5% "03 solutions on the resin was found. A Hg(I1)-Tl(1) solution put on the column in 0.5% "01 was eluted using 5% HKO3. TI(1) appeared in the eluent after 10 column volumes had been collected, and Hg(I1) was eluted shortly thereafter, giving a very slight separation. Separation of Hg(I1)-Tl(1) may be possible using "03 on cation resin by changing parameters such as flow rate, column size, etc. However, practical use of such a procedure would be undesirable from a time consideration. T h e tailing shown by Tl(1) when put on t h e resin in 5% " 0 3 has not
been explained; however, the effect is completely eliminated by reducing the HNOI concentration to less than 1%. Table I contains data obtained from Hg-T1 mixtures separated prior to analyses of the constituents using the ion exchange procedure. REDUCTION PROCEDURE
The use of H?SOIin reducing solutions of Hg(1) and Hg(I1) t o Hg seems to be omitted in current analytical chemistry literature and reference material. While a reference to this reduction applicable to analytical use \vas found ( 6 ) , no conditions for the reduction were given, and no statement relating to the completeness of reaction was found. Although the ion exchange procedure described above was an improvement on existing methods from our standpoint and was used satisfactorily ill this laboratory, the separation times for Hg-TI solutions were 1 to 1.5 hours for thallium elution and another 2 hours for mercury elution. A procedure is described in this section by which quantitative separation of Hg-TI solutions is achieved in a total time for both elements of 10 to 15 minutes. Recovery of both mercury and thallium is quantitative. Experimental. REAGENTS. T h e mercury and thallium solutions and t h e Hg-T1 amalgam used in this procedure are described in the reagent section above. The source of SOz (anhydrous) was a lecture bottle supplied by T h e Matheson Co. PROCEDURE. Hg-T1 solutions containing approximately 1% HX03 were prepared from standard Hg and T1 solutions and by disqolution of Hg-TI amalgam. Aliquots of these solutions were bubbled with SO, for approximately 2 minutes. d white precipitate is formed initially and rapidly goej to a light gray in color. The solutions were boiled gently, using a coldfinger to prevent Hg 1035, until the precipitate was converted to shiny metallic Hg. If the solutions remained cloudly after two minutes of boiling, they were allowed to cool a t room temperature until the supernatant liquid was clear. The solutions were then passed through Whatman No. 41H filter paper to remove the mercury. The filter paper containing the H g was placed in a flask VOL. 38, NO. 7, JUNE 1966
e
827
Table II. Analysis of Hg-TI Mixtures
TI, mg. Hg, mg.Present Found” Present Founda 10.4 52 104 a
10.3 51.7 104
211.3 105.65 21.13
210.9 105.4 20.92
Each number represents the average
of three determinations obtained by taking the given listed amount of T1 or Hg and varying the Hg or T1 concentration to give solutions of approximate Hg: T1 ratios of 20: 1, 1:1, and 1 : 5.
and the Hg was redissolved in ” 0 8 , and the solution was again passed through Whatman No. 41H filter paper to remove the original filter. The filtrate containing the T1 was boiled for 5 minutes to remove excess S02. The analyses of the resulting Hg and T1 solutions were done as previously described in the procedure section. Results and Discussion. T h e ” 0 3 concentration of t h e Hg-T1 solution had no observable effect on reduction of H g in the range of 1% t o 10% H X 0 3 . However, the HKOI was held t o a practical minimum t o prevent redissolution of Hg. The white precipitate observed
initially in the SO2 reduction of Hg(I1) from Hg-T1 solutions was also observed in the SO2 reduction of standard Hg(I1) solutions. A quantity of the white precipitate was filtered from the solution, washed with acetone, and air dried. Examination of the precipitate by emission spectrographic and x-ray diffraction techniques showed a crystalline compound containing H g as the only cation present. When the compound was heated in aqueous solution, the decomposition products identified were H g metal, sulfur dioxide, and sulfate ion. The chemical behavior of the compound corresponded to that of a sulfitomercurate(II), M2 [Hg(SO&], as d e scribed by Remy (7). When warmed, these salts decompose according to the equation [Hg(SO&]Hg SO2 SO4-. Further heating causes the initial finely divided H g to coalesce and form larger drops of mercury. Recovery of mercury and thallium, after separation using this procedure, was quantitative. Emission spectrcgraphic analysis of the T1 and H g solutions after separation was unable to detect any cross-contamination of the two materials.
-
+
+
Table I1 contains data obtained from Hg-T1 mixtures separated prior to determination of the constituents, using this procedure. LITERATURE CITED
(1) Bhatnagar, R. P., Trivedi, R. G., Jour. Indian Chem. SOC.42,513(1965). ( 2 ) Foley, W. T., Osyany, J. M., ANAL. CHEM.33, 1657 (1961). (3) Kolthoff, I. M., Elving, P. J., ed.,
“Treatise on Analytical Chemistry,” Part 11, Vol. 2, Section A by H. Onishi, p. 91, Interscience, New York, 1962. (4) Kolthoff, I. M., Elving, P. J., ed., “Treatise on Analytical Chemistry,” Part 11, Vol. 3, Section A by J. F. Coetzee, p. 306, Interscience, New York, 1962. ( 5 ) Korenman, I. M., iiAnalyticalChemistry of Thallium,” pp. 51-53, Israel Program for Scientific Translations, Jerusalem, 1963. (6!
