(a) Used in dry form - for water-closets, sinks, and cess-pools, copperas (ferrous sulphate), naphthalin (tar balls), lime, and chlorinated lime are preferred because cheap.

(b) Used in solution - for utensils, excreta, bedding, etc., from the sick-room. For basins, chambers, bed-pans, etc., a solution of mercuric bichloride, zinc chloride, or phenol is employed. The zinc chloride is odorless, an obvious advantage over carbolic, whose universally recognized odor suggests unpleasant sickroom experience. In full'strength, Piatt's Chlorides, a proprietary, failed to kill the typhoid bacillus in ten minutes (Hygienic Bulletin No. 82). The bichloride destroys metallic utensils.

The urine, feces, or sputum may be received in, and mixed with, a 3 per cent. solution of carbolic, a 1: 5000 solution of mercuric bichloride, a 1 per cent. solution of zinc chloride, or one-quarter its bulk of quicklime. The mixture should be allowed to stand for half an hour.

(c) Used as gas - for rooms and contents, bedding, clothes, etc., formaldehyd, sulphur dioxide, free chlorine, the creosols of smoke (burning sugar, coffee, brown paper, etc.). It is difficult to find a gaseous disinfectant that will penetrate through bedclothes and mattresses, and into the cracks of a wall or floor.

J. S. Billings says that "terminal disinfection no longer holds a prominent place in the control of infectious diseases, for the reason that by the time the infective agent has disappeared from the person of the patient, it has long since disappeared from the premises and surroundings."