Ores in which the copper is present as oxide or carbonate are soluble in sulphuric or hydrochloric acids, ferrous chloride, ferric sulphate, ammoniacal compounds and sodium thiosulphate.
The solubility of the various alums in water varies greatly, sodium alum being readily soluble in water, whilst caesium and rubidium alums are only sparingly soluble.
Being thus soluble in salt water it cannot, of course, be salted out like common soaps; but if a very concentrated salt solution is used precipitation is effected, and a curd soap is separated so hard and refractory as to be practically useless.
This theory being accepted, it is evident that a small quantity of water, by successive dissolution and deposition of a substance capable of existing in a more soluble and in a less soluble form, is able to bring about the crystallization of an indefinitely large quantit y of material.
Ammonium cyanide, NH 4 NC, a white solid found to some slight extent in illuminating gas, is easily soluble in water and alcohol, and is very poisonous.
Cadmium sulphide, CdS, occurs naturally as greenockite (q.v.), and can be artificially prepared by passing sulphuretted hydrogen through acid solutions of soluble cadmium salts, when it is precipitated as a pale yellow amorphous solid.
Metallic chlorides, as a class, are readily soluble in water.
The hydroxide, In(OH) 3j is prepared, as a gelatinous precipitate, by adding ammonia to any soluble indium salt.
It may be separated from the quinoline which accompanies it by means of the difference in the solubility of the sulphates of the two compounds, isoquinoline sulphate being much less soluble than quinoline sulphate.
It will not dissolve in water as gums do, but it is soluble in alcohol, as resin usually is.