The oxide and carbonate, in doses of a grain and less, exert an astringent and somewhat sedative action on the gastro-intestinal tract, markedly lessening its secretions. The sulphate, in small, non-irritant doses, is still more astringent. All zinc compounds have a tendency to excite nausea and irritation of the stomach; the oxide and the carbonate, though tasteless, show this effect when given in doses of from 1 to 5 gr. and upward. The soluble salts have a styptic metallic taste, and the sulphate, in doses of 5 to 10 gr. and upward, acts as a prompt and thorough emetic without much nausea or prostration, though often with diarrhoea: this action is not purely a local one, because it is equally produced by intravenous injection of the salt. Emesis, however, is not a constant effect, for if the drug be taken at first in small doses and continued regularly, a certain tolerance is established, and then 10 to 20-gr. doses may be taken without disorder of the stomach. Caution is required in the continuance even of small doses, since they have been said to cause ulceration of mucous membrane, and ultimately symptoms like those of lead-poisoning, such as emaciation, anaemia, debility, fetor of breath, constipation, and colic, also tremor, paralysis, etc. Symptoms of acute irritant poisoning, such as pain, vomiting, convulsion, and collapse, have followed doses of 30 to 60 gr., and sometimes concentrated solutions have caused death (Medical Times, ii., 18G2, p. 252), but the salt has rarely proved fatal, because of its being so soon rejected; persons have recovered after taking an ounce or even more.

The chloride is much more corrosive in character, and is unsuited for internal use - 5 to 10 gr. have produced severe irritant symptoms. It has been a not infrequent source of fatal poisoning in the form of Sir W. Burnett's disinfecting fluid, which is an impure solution of it, somewhat oily in character, and either colorless or of yellowish tinge, from the presence of some ferric oxide: it has been mistaken for fluid magnesia, for mineral waters, and for pale ale, the fact of its frothing up when shaken contributing to its resemblance to the last-mentioned: one fl. oz. has been found to contain from 100 to 372 gr. of solid chloride (Taylor), 200 gr. (R. W. Smith), and less than that quantity has proved fatal, though not invariably.