These combine chemically with albumin to form precipitates of metallic albuminates, which make an impenetrable pellicle.

Thus the metallic salts have little penetrating power, and are readily destroyed by the body fluids.

Those most employed as antiseptics and disinfectants are:

Of mercury - mercuric chloride and mercurophen; also, slightly, in ointment form, ammoniated mercury and mercuric oxide.

Of gold - sodium aurate, reported by Verhoeff (1906) as of great efficacy and little toxicity. Of silver - the nitrate, protargol, argyrol, etc. Of copper and iron - the sulphates. Of zinc - the sulphate and the chloride. Of aluminium - the acetate, made fresh in solution. Of bismuth - the subiodide, and perhaps slightly the subnitrate and other salts. The pharmacology of the metals is considered further on.