ained artificially, as a white gelatinous
precipitate which shrinks greatly on drying, by mixing solutions of sodium
hydrogen phosphate, ammonia, and calcium chloride. Crystals may be obtained
by heating di-calcium pyrophosphate, Ca_2P_2O_7, with water under pressure.
It is insoluble in water; slightly soluble in solutions of carbonic acid
and common salt, and readily soluble in concentrated hydrochloric and
nitric acid. Of the acid orthophosphates, the mono-calcium salt,
CaH_4(PO_4)_2, may be obtained as crystalline scales, containing one
molecule of water, by evaporating a solution of the normal salt in
hydrochloric or nitric acid. It dissolves readily in water, the solution
having an acid reaction. The artificial manure known as "superphosphate of
lime" consists of this salt and calcium sulphate, and is obtained by
treating ground bones, coprolites, &c., with sulphuric acid. The di-calcium
salt, Ca_2H_2(PO_4)_2, occurs in a concretionary form in the ureters and
cloaca of the sturgeon, and also in guano. It is obtained as rhombic plates
by mixing dilute solutions of calcium chloride and sodium phosphate, and
passing carbon dioxide into the liquid. Other phosphates are also known.

_Calcium monosulphide_, CaS, a white amorphous powder, sparingly soluble in
water, is formed by heating the sulphate with charcoal, or by heating lime
in a current of sulphuretted hydrogen. It is particularly noteworthy from
the phosphorescence which it exhibits when heated, or after exposure to the
sun's rays; hence its synonym "Canton's phosphorus," after John Canton
(1718-1772), an English natural philosopher. The sulphydrate or
hydrosulphide, Ca(SH)_2, is obtained as colourless, prismatic crystals of
the composition Ca(SH)_2.6H_2O, by passing sulphuretted hydrogen into milk
of lime. The strong aqueous solution deposits colourless, four-sided prisms
of the hydroxy-hydrosulphide, Ca(OH)(SH). The disulphide, CaS_2 and
pentasulphide, CaS_5, are formed when milk of lime is boiled with flowers
of sulphur. These sulphides form the basis of Balmain's luminous paint. An
oxysulphide, 2CaS.CaO, is sometimes present in "soda-waste," and
orange-coloured, acicular crystals of 4CaS.CaSO_4.18H_2O occasionally
settle out on the long standing of oxidized "soda- or alkali-waste" (see
ALKALI MANUFACTURE).

_Calcium sulphite_, CaSO_3, a white substance, soluble in water, is
prepared by passing sulphur dioxide into milk of lime. This solution with
excess of s