MINERAL ACIDS, in medicine. The ordinary mineral acids are sulphuric (oil of vitriol), nitric (aqua fortis), hydrochloric (rnuriatic acid), phosphoric, chromic, and carbonic acids. Of these the latter only is usually regarded as a gas, that beiug its ordinary condition, but all the others are gases or vapors at certain temperatures, except phosphoric and chromic which on being heated change in composition. Concentrated sulphuric acid boils (in other words becomes a vapor) at 620° F., and concentrated nitric at 184° F. Hydrochloric acid is a solution of a gas in water, and has constantly varying degrees of strength. An aqueous solution boiling at 230° F. gives off a vapor which contains 20.22 per cent of anhydrous acid gas dissolved in 79.78 per cent of water, which may be condensed in a receiver. A more coucentrated solution when heated yields at first only gas; as it gets weaker by parting with the gas, water begins to pass off along with it. These acids have various uses in medicine. Sulphuric, nitric, chromic, and hydrochloric acids in a concentrated state are powerfully corrosive, and on this account nitric acid is used in surgery as an escharotic, to destroy warts and other excrescences or diseased growths or unhealthy tissues. It has the property of only injuring the tissue as far as it destroys it, leaving a wound which heals easily. Sulphuric acid, on the con trary, produces an inflammation which does uot readily subside, while hydrochloric acid used as an escharotic produces sloughing, sometimes of a dangerous character. Chro mic acid which is ordinarily a crystalline solid of a beautiful crimson color is soluble in water, and its solution. of a proper strength, is also used as an escharotic in surgery, and
is generally preferred to nitric acid, being rather more manageable. It is also used, in weaker solutions, as an application to the gums in scrofulous patients, when there is a tendency to ulceration, and in other ill-conditioned states of the system, and also as a styptic for arresting surface hemorrhage. It is not administered internally. Sulphuric acid in a diluted form is sometimes employed as a tonic, and its various salts are many of them valuable medicines. See sulphates in SULPHURIC A CID, ante. Dilute nitric acid is given as a medicine in several affections. It sometimes succeeds in intermittent fever when quinine is contra-indicated, and has been given in dysentery, on the recom mendation of Hope. In some forms of dyspepsia and mal-assimilation it is useful in assisting digestion and improving nutrition. In combination with hydrochloric acid, in the form of diluted aqua-regia, it is oft,eu successfully used in cases of jaundice, and also in some forms of dyspepsia, hydrochloric acid being a natural ingredient of the gastric juice. Dilute nitric acid has been used with benefit in diabetes mellitus, and it is stated that in large doses, largely diluted in water, it has cured several cases of diabe tes insipidus. It has also been successfully used in scrofula and glandular enlargements. See CARBONIC ACID, NITRIC ACID, HYDROCHLORIC ACID, and phosphoric acid 1D Puos PHORUS.