~Ammonic Oxalate~ (Am_{2}C_{2}O_{4}.2H_{2}O) is used chiefly for the separation of lime. The solution is made by dissolving 15 grams of the salt in 100 c.c. of water. ~Ammonic Sulphide~ may be purchased in the state of a strong solution. It is yellow, and contains the disulphide, S_{2}Am_{2}. It serves the same purpose as is obtained by passing a current of sulphuretted hydrogen through an ammoniacal solution; but has the disadvantage of loading the solution with sulphur, which is precipitated when the solution is subsequently acidified. It is useful for dissolving the lower sulphide of tin (SnS). ~Baric Carbonate~ (BaCO_{3}) is sometimes used for precipitating the weaker bases. It should be prepared when wanted by precipitating a solution of baric chloride with ammonic carbonate and washing. The moist precipitate is used without drying. ~Baric Chloride~, BaCl_{2}.2H_{2}O.--A crystallised salt, soluble in 2-1/2 parts of water. It is used for the detection and separation of sulphates. Make a 10 per cent. solution. "~Black Flux.~"--A mixture of finely divided carbon with carbonate of potash or with carbonates of potash and soda. It is prepared by heating tartar or "rochelle salt" until no more combustible gas is given off. One gram will reduce about 2 grams of lead from litharge. ~Borax~, Na_{2}B_{4}O_{7}.10H_{2}O.--It is chiefly used as a flux in dry assaying, as already described. It is also used in testing before the blowpipe; many metallic oxides impart a characteristic colour to a bead of borax in which they have been fused. ~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.