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

CUPRIC AND CUPROUS BROMIDES. 73

Thallous hydroxide forms light-yellow crystals which are

readily soluble in water; the aqueous solution of these crystals is

strongly alkaline, its electrical conductivity being nearly the same

as that of a sodium hydroxide solution of the same concentration.

Filter paper moistened with thallous hydroxide serves as a re-

agent for detecting the presence of ozone; brown thallic oxide is

formed.

Reactions of Thallous Salts. Solutions of thallous salts when

treated with iodide solutions give a yellow, very difficultly soluble

precipitate of thallous iodide (analogous to Agl); with chloro-

platinic acid, they give light-yellow, difficultly-soluble thallium

chloroplatinate, Tl 2 [PtCl 6 ] (analogous to K 2 [PtCl 6 ]); with ammo-

nium sulphide, or hydrogen Sulphide together with sodium acetate,

they give a deep-brown precipitate of thallous sulphide (analogous

to Ag2S).

Hydrated Thallic Oxide (analogous to hydrated ferric oxide).

Oxidize a part of the thallous nitrate solution by the addition of

an excess of bromine, and precipitate the resulting brown solution

by adding concentrated ammonia. The very fine precipitate

settles slowly. Wash it by decantation with water containing

ammonia until the decanted liquid is free from bromine, and

then drain it upon a filter. Dry the product in a desiccator over

sulphuric acid, for at higher temperature it loses water and becomes

thallic oxide.

Thallic Thallous Chloride, TICh • 3 TICl. Dissolve a small quan-

tity of hydrated thallic oxide, or the anhydrous oxide, in a little

hydrochloric acid, dilute with about one-third of a test-tubeful of

water, an equal volume of normal oxalic acid solution and boil,

whereby carbon dioxide will escape. After heating a few minutes,

allow the contents of the test tube to cool: iridescent small

crystalline flakes of the above-named salt will be deposited.

(b) Halogen Compounds.

37. Cupric and Cuprous Bromides.

Dissolve 16 g. of cupric oxide in a solution of hydrobromic acid

containing 33 g. of pure HBr. Filter the resulting solution and

evaporate it to a small volume, whereby the color becomes very