Laboratory Methods of Inorganic Chemistry, 2nd English Ed. 1928

BARIUM TRITHIOCARBONATE. 137

phosphorus trichloride from a dropping funnel. After the re-

action is over, transfer the liquid to a distilling flask and distil off

the hydrochloric acid and water under reduced pressure (p. 8).

The phosphorous acid remains behind as a colorless, fibrous,

crystalline mass which is hygroscopic and therefore must be kept

in well stoppered vessels.

THIO-ACIDS AND THEIR SALTS.

98. Potassium Trithiocarbonate Solution (Reagent for Nickel).
    Divide 50 c.c. of a 5% solution of potassium hydroxide into two
    equal portions; saturate one with hydrogen sulphide and mix it
    with the other portion. Shake this solution of potassium sulphide
    vigorously with 2 c.c. of carbon bisulphide for five minutes and
    then pour it through a filter which has been moistened with water.
    The bright, orange-red solution contains K 2 CS 3 , and is an extremely
    delicate reagent for nickel. With concentrated ammoniacal solu-
    tions of nickel salts, it gives a brownish-black precipitate; with
    dilute solutions, a dark brown coloration.
    Determine the sensitiveness of the test: Start with 1 or 2 c.c. of
    a 0.0002-normal nickel solution, and if this gives a distinct reaction,
    dilute ten times and test again, and continue in this way until the
    limit of sensitiveness is reached.
    In order to find to what extent cobalt interferes with the re-
    action, test solutions containing 1, 2, 10, 50 and more atomic
    equivalents of cobalt for each atom of nickel.


99. Barium Trithiocarbonate.
    Dissolve 32 g. of crystallized barium hydroxide in 100 c.c. of hot
    water. Place one half of the solution in a closed flask and saturate
    it with hydrogen sulphide, whereby barium sulphydrate is formed;
    then add the other half of the original barium hydroxide solution.
    Shake the resulting solution of barium sulphide with 8 g. of carbon

bisulphide, whereupon barium trithiocarbonate, BaCS 3 , precipi-

tates as a yellow, crystalline powder. Drain the precipitate, wash

it with a little water, then with 50% alcohol, and finally with pure
alcohol; and dry it in a warm place (on top of the hot closet). As

the alcohol used for washing runs into the filtrate, more of the

barium trithiocarbonate precipitates. Yield, 12 to 15 g.