Many of the acids and alkalies are active antiseptics. In weak solutions hindering the organisms in their growth, in stronger solutions killing them by withdrawing water, by coagulation of protoplasm, or by other physico-chemical interchange.

For the acids, those that dissociate readily are more actively germicide, thus tri-chlor-acetic acid, by reason of its ready power of dissociation, is almost as efficient a germicide as the much more powerful nitric acid. Acetic and formic acids are relatively weak because of their diminished powers of dissociation.

Sulphuric, nitric, acetic, boric, and arsenous acids are the acids more commonly employed, while sodium, potassium, and ammonium hydrates, the various soaps, etc., are the alkalies used.

As these bodies for the greater part are considered in this work more in detail under the head of Caustics, etc., they are best consulted in those chapters. Only a few will be considered in this place.