PRECIPITATION OF MERCURIC CHLORIDE WITH DITHIANE' JAMES B. SCHROYER" and ROBERT M. JACKMANa Adrian College, Adrian, Michigan
ADDI~ products O N of metallic salts with heterocyclic
sodium hydroxide and a plentiful supply of hydrogen compounds like dioxane, C,HSO2,and dithiane, C~HSSZ,sulfide. To prevent premature reaction between .the have been studied in recent Of these, the com- sodium hydroxide and the ethylene bromide (see second pound HgCl2.C&SZ is distinguished by its slight solu- step described above), the absolute alcohol and ethylene bility in water. From dilute solutions of mercuric chlo- bromide were mixed in small portions and thoroughly ride dithiane precipitates shining, colorless, plate-like chilled. The pulverized sodium hydroxide was added crystals; from more concentrated solutions, the precipi- to the chilled mixture just before addition to the sodium bisulfide solution. Bouknight and Smith's instructions tate is white and without luster. Although several other common metals form similar produce from 8 to 10 grams of dithiane. A batch three compounds, these compounds are not precipitated from or four times as large may he successfully prepared by aqueous solution of the concentrations ordinarily met appropriate changes. - Our average yield was 32 per with in inorganic analytical work. This fact suggests cent, m. p. 109-110.5". The reagent used in precipitathe possibility of specifically precipitating mercury in tion of mercury was a 2 per cent solution of dithiane in this form. This investigation was carried out to deter- 95 per cent ethyl alcohol. mine whether dithiane can he used satisfactorily as a specific reagent for the detection and the determination SPECIFIC NATURE OF THE REAGENT of mercuric mercury in the presence of other common The dithiane reagent was tested with 63 "unknown" ions. The results indicate that. within certain limits.' solutions which hazbeen prepared for a course in qualidithiane is very satisfactow for this ~uruose. tative analysis. These sokions contained all the ;omPREPARATION OF THE REAGENT mon positive ions in concentrations from 5 to 200 mg. Dithiflne was prepared by the method developed by per ml. In each case hydrochloric acid was added to Bouknieht and Smith.5 Their brief instructions are make vossible the uresence of mercuric chloride and to repeatei here, with comments, since dithiane is not provide the opt&m conditions for precipitation (see Tables 3 and 4). This treatment, of course, removed the available on the market a t present. ions of silver and mercurous mercury, together with Twenty grams of pnlverised sodium hydroxide in 50 ml. of absolute aloohol was treated with hydrogen sulfide until the much lead. The filtrate or centrifugate was then tested sodium sulfide initially formed redissolved. A mixture of 20 g. with dithiane solution. I n all cases where mercuric of pulverized sodium hydroxide and 84.6 g. of ethylene bromide in mercury was present it was precipitated a t once as the 150 ml. of absolute alcohol was added in small portions with white HgCl2C4H8SZ.No precipitate was produced in shaking. The mixture wss cooled and reconnected to the hydrogen sulfide generator for about three hours. A small amount any case where mercuric mercury was absent. Selected of solid sodium hvdroxide was added and the dithiane distilled typical cases are shown in Table 1. Numbers within the with steam: best yield obtained, 45 per cent of the theoretical; table indicate concentrations of the ions in mg. per ml. m. p., 110-111. After the insoluble chlorides of the Group I metals were removed, the only interference encountered in a 2NaOH + H d N&S ~HBO chloride solution was due to large concentrations of copNalS + H B 2NaHS per. Copper without mercury is not precipitated by dithiane, but large concentrations of copper give a pink 2NaHS + 2CH2BrCHsBr 2NaBr color to the mercuric chloridedithiane precipitate. successful preparation of the sodium hisulfide in the This interference due to copper is minimized by low hydrochbric acid concentrations. Quantitative study initial depends upon using very finely of the worst case encountered showed the presence of From a report submitted by Robert M. Jackman on Number 6 in a series of chemical investigations conducted hy Adrian Col- 0.6 mg. precipitated with loomg. of mercury. Several other positive ions not ordinarily included in lege senior students. Present address: Hiram College, Hiram, Ohio. courses in qualitative analysis were tested separately a Present address: Anderson Laboratories, Inc., Adrian, Miehigan. with the dithiane reagent. Platinum and palladium ' REEINBOLDT, H.. A . LUYKEN, AND H. SCEMITTMIW, J. prakt. gave yellow precipitates from a chloride solution. CeChen., 149, 30-44 (1937). 6 B O U K N I GJ. ~ ,W., AND G. McP. SMITE, J. Am. Chem. Soc., rium, lithium, titanium, and uranium gave no reaction. Mercuric sulfate gives a white precipitate of moderate 61, 2 8 4 0 (1939).
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