Its principal action is as an antiseptic and disinfectant.
The perchloride of mercury is another very powerful antiseptic used in solutions of strength I in 2000, I in 1000 and 1 in 500.
Gum benzoin, which contains from 12 to 20% of benzoic acid, is used in medicine as the essential constituent of benzoated lard, Adeps benzoatus, which owes its antiseptic properties to benzoic acid; and in friar's balsam, Tinctura benzoini composita, which is an ancient and valuable medicament, still largely used for inhalation in cases of laryngitis, bronchitis and other inflammatory or actually septic conditions of the respiratory tract.
No case' of so-called " spontaneous generation " has withstood rigid investigation; but the discussion contributed to more exact ideas as to the ubiquity, minuteness, and high powers of resistance to physical agents of the spores of Schizomycetes, and led to more exact ideas of antiseptic treatments.
It is a more powerful antiseptic than carbolic acid, but its insolubility prevents its being used for the same purposes.
It is, however, a useful superficial caustic and antiseptic. All copper compounds are poisonous, but not so harmful as the copper arsenical pigments.
But by the addition of some antiseptic to the ointment its defensive action would be converted from passive to active, and its power to prevent infection would become greater; and if inflammation had already set up in the skin, the addition of opium, belladonna, or cocaine would lessen local pain; and an astringent, either metallic or organic, would restrain inflammation and accelerate repair.
Used externally it is an antiseptic and disinfectant, and is used 5 to 10% in ointments in the treatment of chronic skin diseases such as psoriasis and eczema of a sub-acute character.