Exercise 76. Barium Trithiocarbonate

The barium salt is easier to obtain in solid form than is the corresponding potassium salt. Dissolve 15 g. of crystallized barium hydroxide in 50 cc. of warm water and divide the solution into two equal parts. Completely saturate the one portion (in a stoppered flask) with hydrogen sulfide and then add the other portion, thus forming a solution of barium sulfide. Add about 1 cc. of carbon disulfide and shake from time to time. It is better to add the carbon disulfide by conducting a current of coal gas (from the laboratory gas supply) through a little carbon disulfide in a wash flask and thence into the solution of barium sulfide. The barium salt precipitates as a yellow crystalline powder. The filtered precipitate should be washed first with water, then with half alcohol, finally with pure alcohol and dried on a hot plate. A second crop of crystals may be obtained by allowing the wash alcohol to drain into the mother liquor. 

Dissolve 20 g. of cuprous chloride, CuCl, in the least possible volume of concentrated hydrochloric acid. Cool the solution in ice and slowly add 500 cc. of concentrated ammonia. Keeping the temperature at 0°, add 55 g. of carbon disulfide and shake vigorously at frequent intervals. After standing some 6 days in an ice box at approximately 0°, shining green crystals of the thio-carbonate separate from the solution. Filter off these crystals, wash them with cold water, and quickly dry them on paper. The potassium salt can be made with slight modifications of these directions. 

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