CHLORIDE OF AMMONIUM IN" CHEMISTRY. 
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niac; that portion of the oxide which has not been reduced 
by the heat before the chloride of ammonium begins to act 
is converted into chloride of silver. Antimoniuret of silver 
(the native coarse grained mineral from Wolach, Ag 2 Sb) is 
but imperfectly decomposed by chloride of ammonium; by 
repeated treatment it is most probable that metallic silver 
would remain, since the more frequently it is calcined with 
chloride of ammonium, the more the antimoniuret of silver 
decreases in weight, and the residue becomes less brittle. 
Lead Compounds. — Oxide of lead, calcined with chlo- 
ride of ammonium, is converted into chloride of lead, which, 
on the access of air and the repeated addition of chloride of 
ammonium, may be entirely volatilized. Sulphuret of lead, 
calcined with sal-ammoniac, gives a fused blackish-brown 
residue, which is a compound of chloride and sulphuret of 
lead, and which, on the access of air, gives oft* dense va- 
pours of chloride of lead, and may be wholly volatilized by 
the repeated addition of sal-ammoniac. 
Oxide of Zinc is entirely volatilized as chloride of zinc 
when mixed with chloride of ammonium, but with great 
difficulty when the air is excluded. 
Sulphate of zinc, deprived of its water of crystallization 
and calcined with chloride of ammonium, froths up very 
considerably. By repeated treatment with chloride of am- 
monium the residue can be wholly volatilized. 
Oxide of Chromium and Crhomates. — The first experien- 
ces no change by calcination with chloride of ammonium, but 
the alkaline chromates leave a mixture of oxide of chromi- 
um and alkaline chloride ; the latter dissolves on treatment 
with water, while the former is left undissolved. The alka- 
line chromates may be easily and accurately analysed by 
this method. The double sulphate of potash and oxide of 
chromium, after being deprived of its water, is converted in- 
to a mixture of oxide of chronium and chloride of potassi- 
um on ignition with sal-ammoniac. 
Silicic Acid. — Silicic acid, which has not been heated too 
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