Properties : Copper sulphate forms large, transparent, deep-blue crystals, odorless, having a nauseous, metallic taste. Copper sulphate is freely soluble in water (1:2.2) but only slightly soluble in alcohol (1:400).

Incompatibilities: Copper sulphate is incompatible with soluble salts of lead, which precipitate the insoluble sulphate of lead; with fixed alkalies and alkaline carbonates, which precipitate copper hydroxid or copper carbonate; with iodids, which form insoluble cuprous iodid with liberation of iodin, and with vegetable astringents containing tannin.

Action and Uses: Copper sulphate is astringent in small doses and irritant in large doses, producing nausea and vomiting. Copper sulphate in small amounts exerts-a germicidal action in water containing algae, fungi or bacteria of the colon group; but when organic matter is abundantly present the germicidal action is greatly weakened. Externally copper sulphate acts as an astringent, stimulant or mild caustic according to the strength of the application.

Copper sulphate is used as a mild caustic in trachoma. It was formerly much used as an astringent in conjunctivitis. It is sometimes used as an emetic but is not to be recommended except in phosphorus poisoning, in which it acts by precipitating an insoluble compound of phosphorus and copper. It is occasionally prescribed for chronic diarrhea.

Dosage: As an astringent in diarrhea, 0.01 gm. or 1/5 grain; as an emetic, 0.3 gm. or 5 grains, not to be repeated.

As a caustic it is applied as the solid crystal or in pencils made by fusing 1 part of potassium alum and 2 parts of copper sulphate. When applications are made to trachomatous lids the affected parts of the everted lid should be touched lightly with the copper stick and the eye washed out afterward with lukewarm water. Collyria containing from 1 part in 1,000 to 1 in 100 may be used.