~Calcium Chloride.~--The crystallised salt is CaCl_{2}.6H_{2}O; dried at
200° C. it becomes CaCl_{2}.2H_{2}O, and when fused it becomes
dehydrated. The fused salt, broken into small lumps, is used for drying
gases. It combines with water, giving off much heat; and dissolves in a
little more than its own weight of water. Strong solutions may be used
in baths in which temperatures above the boiling-point of water are
required. One part of the salt and 2 of water give a solution boiling at
112°, and a solution of 2 parts of the salt in 1 of water boils at 158°.
The salt is very little used as a reagent.
~Calcium Fluoride~ or "~Fluor Spar~," CaF_{2}.--The mineral is used as a
flux in dry assaying; it renders slags which are thick from the presence
of phosphates, &c., very fluid. Mixed with hydrochloric acid it may
sometimes be used instead of hydrofluoric acid.
~Calcium Carbonate~, CaCO_{3}.--It is precipitated in a pure state by
ammonic carbonate from a solution of calcium chloride. It is used for
standardising. In the impure state, as marble or limestone, it is used
in the preparation of carbonic acid.
~Calcium Hydrate~ or ~"Lime Water."~--This is used in testing for carbon
dioxide and in estimating the amount of that gas present in air. It may
be made by slaking quicklime and digesting the slaked lime with water.
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