This is water impregnated with gaseous ammonia. As it is much more used as an external irritant than as a stimulant internally, it will be more particularly treated of among the rubefacients. Its effects upon the system are essentially the same as those of the carbonate above described, and it may be used for the same purposes; but, as it would be more likely, if given in excess, to irritate or inflame the stomach, the salt is generally preferred. As a stimulant antacid, it is sometimes used in heartburn, and in sick-headache dependent on acidity of stomach; and it has had considerable reputation as an antidote to the poison of serpents, being applied for this purpose to the bite, as well as taken internally. There is some reason, however, to doubt its efficiency; and, though it may be employed, it should never be relied on to the exclusion of more efficient measures. When taken by accident undiluted, or insufficiently diluted, it produces severe inflammation of the mucous membrane of the mouth, fauces, and stomach, and may even vesicate or act corrosively. The antidotes are the vegetable acids. Much more caution is requisite in applying this to the nostrils, in order to revive fainting persons, or to rouse from positive syncope, than the carbonate, in consequence of the causticity of the vapour. Several instances of severe inflammation of the air-passages are on record from this cause, some of which proved fatal. In one of the instances, the vapour of the ammonia was inhaled as an antidote to hydrocyanic acid. The dose is from ten to thirty drops, which should be given in one or two fluidounces of water.

Water of ammonia, much diluted, has recently been employed externally, with a view to constitutional effect, by Mr. John Grantham, of Kent, England, with great apparent advantage in certain cases. The affections in which it seemed to be most efficacious were purpura hemorrhagica, with internal hemorrhages from various points, and of a most serious character, and scarlatina with great general depression; but the remedy is probably applicable to all cases of low disease connected with a morbid state of the blood. He applies, over the whole surface of the body, by means of a sponge, a mixture of from one and a half to two fluid-ounces with two quarts of water, heated to 120°. (Med. Times and Gaz., May, 1860, p. 521).