ting
with carbon. Concentrated sulphuric acid dissolves this oxide, forming
a yellowish solution and ozone. By suspending the precipitated cerous
hydroxide in water and passing chlorine through the solution, a
hydrated form of the dioxide, 2CeO2.3H2O, is obtained, which is
readily soluble in nitric and sulphuric acids, forming ceric salts,
and in hydrochloric acid, where it forms cerous chloride, with
liberation of chlorine. A higher hydrated oxide, CeO3.xH2O, is formed
by the interaction of cerous sulphate with sodium acetate and hydrogen
peroxide (Lecoq de Boisbaudran, _Comptes rendus_, 1885, 100, p. 605).

Cerous chloride, CeCl3, is obtained when the metal is burned in
chlorine; when a mixture of cerous oxide and carbon is heated in
chlorine; or by rapid heating of the dioxide in a stream of carbon
monoxide and chlorine. It is a colourless substance, which is easily
fusible. A hydrated chloride of composition 2CeCl3.15H2O is also
known, and is obtained when a solution of cerous oxide in hydrochloric
acid is evaporated over sulphuric acid. Double salts of cerous
chloride with stannic chloride, mercuric chloride, and platinic
chloride are also known. Cerous bromide, 2CeBr3.3H2O, and iodide,
CeI3.9H2O, are known. Cerous sulphide, Ce2S3, results on heating
cerium with sulphur or cerium oxide in carbon bisulphide vapour. It is
a red infusible mass of specific gravity 5.1, and is slowly decomposed
by warm water. The sulphate, Ce2(SO4)3, is formed on dissolving the
carbonate in sulphuric acid, or on dissolving the basic sulphate in
sulphuric acid, in the presence of sulphur dioxide, evaporating the
solution, and drying the product obtained, at high temperature (B.
Brauner, _Monatshefte_, 1885, vi. 793). It is a white powder of
specific gravity 3.912, easily soluble in cold water. Many hydrated
forms of the sulphate are known, as are also double salts of the
sulphate with potassium, sodium, ammonium, thallium and cadmium
sulphates. Ceric fluoride, CeF4.H2O, is obtained when the hydrated
dioxide is dissolved in hydrofluoric acid and the solution evaporated
on the water bath (B. Brauner). The sulphate, Ce(SO4)2.4H2O, is formed
when the basic sulphate is dissolved in sulphuric acid; or when the
dioxide is dissolved in dilute sulphuric acid, and evaporated _in
vacuo_ over sulphuric acid. It forms yellow crystals soluble in water;
the aqueous solution on stan