ANALYTICAL CHEMISTRY
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The acidity provided by the digestion mixture appears to be quite satisfactory in the above method. The tellurium oxide, oxychloride, and tellurous acid do not have sufficient vapor pressure to allow loss of tellurium during the digestion. Care should be taken that the digestion does not proceed to dryness, the perchloric acid digestion mixture becomes colorless, the entire procedure is carried out within a 24 hour period, the phosphoric acid and indicator are added just prior to the backtitration with the potassium dichromate, and the sample is completely dissolved before the perchloric acid is added. The excess ferrous ion is easily observed due to a color change in the sohtion. RESULTS
Table I summarizes the results obtained on blanks and on titration of tellurite stock solution, prepared according to DeMeio ( 1 ) with, and without, perchloric acid digestion. A number of organotellurium compounds were analyzed and the results are summarized in Table 11. The anisyl compounds were previously analyzed gravimetrically by Morgan and Kellett (IO). Halogen analysis, carried out in this laboratory, as well as some carbon and hydrogen analyses are included for comparison. To indicate the usual deviation in a series of samples of a given com-
pound, the results of the analysis of p-(n-butoxy)phenyl tellurium trichloride are included in Table 111. ACKNOWLEDGMENT
The authors gratefully wish to acknowledge partial support of the above work by the Office of Naval Research. LITERATURE CITED (1) (2) (3) (4) (5)
DeMeio, R. H., ANAL.CHEM.,20, 488 (1948). Drew, H. D. K., J. Chem. SOC., 1934, 1796. Drew, H. D. K., and Porter, C. R., Ibid., 1929, 2091. Evans, B. S.,Analyst, 63, 874 (1938). Johnson, R. A. and Frederickson, D. R., ANAL.CHEM.,24, 866
(1952). (6) Johnson, R. A, and Kwan, F. P., Ibid., 23, 651 (1951). (7) Lang, R., 2. anal. chem., 128, 484 (1948). ( 8 ) Lenher, V., Proe. Am. Phil. Soc., 65, 33 (1926). (9) Lenher, V., and Wakefield, H. F., J . Am. Chem. SOC., 45, 1423 (1923). (10) Morgan, G. T., and Kellett, R. E., J . Chem. SOC., 1926, 1084. (11) Smith, G. F., “Mixed Perchloric, Sulfuric and Phosphoric Acids.” Columbus. Ohio. G. F. Smith Chemical Co.. 1942. (12) Tsao, E. T., Chem. I n d . ( C h i n a ) , 10, KO. 2, 15 (1935); C . A . , 30, 2135’ (1936). (13) Willard, H. H., and Young, P. J., J . Am. Chem. SOC., 52, 553 (1930). (14) Willis, U. F., Analyst, 66, 414 (1941).
RECEIVED for review March 17, 1052. Accepted October 17, 1952
Precipitation in Homogeneous Solution Separation and Determination of Lead PHILIP J. ELVINGI AND WALTER C. ZOOI
