ANALYSIS OF MERCURY(I1) SALTS WITH THIOACETAMIDE NORBERT ISENBERG, ELAINE M. PERLMAN, RUBY L. PURYEAR, a d SONIA A. SPARKSSkidmore College, Saratoga Springs, New York
THE reaction between thioacetamide and mercury (11) salts leads t o a variety of precipitates depending upon the concentration of the thioacetamide, the pH of the solution, and the type of acid present in the reaction mixture ( I ) . I n order to learn whether the orange or the brown compounds formed under the conditions of a standard analytical procedure (%) would interfere with the analysis of mercury the fonoming experiments were performed: The hydrogen ion concentration was adjusted to 0.3 M and precipitation with an excess of an 8% solution of thioacetamide was carried out. An oranee amide (3). This orange precipitate dissolved partially in 6 M potassium hydroxide (5) and when the latter solution was neutralized with hydrochloric acid, a black precipitate reappeared. This black precipitate proved to be mercuric sulfide. It was thus shown that the behavior of the orange substance does not differ from that of the black mercuric sulfide for analvtical DurDoses at this s t e in ~ the ~rocedure. " when the hvdroeeu ionconcen&ion was adjusted to 2 M (4) the color of the precipitate obtained from the treatment with thiOacetamide was dark and its behavior in subsequent separation procedures was the same as that described for the orange compound. The adjustment of the hydrogen ion conof 2 M was made because the buffering
' Presented a t the Third Annod Intercollegiate Chemical Symposium sponsored by the Eastern New York Section of the American Chemical Society a t Siena College, Loudonville, New York, May 17, 1958.
action of acetateliberated in the hydrolysis of thioacetamide decreases the acidity (5). Neither the orange nor the dark brown compound dissolved in 6 M nitric acid. This allows the separation of cadmium, bismuth, copper, and lead salts from the mercury(I1) salt. The orange as well as the dark brown precipitate dissolved in aqua regia and gave positive tests with stannous chloride. Initial H+ 0 . 3 A4
Solution tested Rearent Omnae mereunr(I1) oom- Stannous
Obsmation Light gray ore-
. . It may thus be concluded that even though a variety of colored compounds are formed when thioacetamide is used to precipitate mercury(I1) sulfide there seems t o be no interference with the usual analytical procedures at this point. It is also confirmed that an adjustment of the initial hydrogen ion concentration to 2 M is desirable when is substituted for hy.-. . thioacetamide . . . drogen ln the analys's. LITERATURE CITED (1) Vozzil, JOHN F., J . CHEM.EDUC., 35, 145 (1958). z,QUalitBtiVe R,,AND WmREN C. Analysis and Chemical Equilibrium," 4th ed., Henry Holt & Go., Inc., 1954, p. 421. (3) NORDMAN,JOSEPH, "Qualitative Testing and Inorganic Chemistry," John Wiley & Sons, Inc., New York, 1957, p. 269. (4) GUNNING, HARRYE., J. CHEM.EDUC.,32, 258 (1955). (5) MOELLER,THERALD,"Qualitative Analysis," 1st ed., McGraw-Hill Book Co., Ino., New York, 1958, p. 451.
(2) HooNEss, T,
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