ACIDUM NITRICUM DILUTUM. L. Acidum Nitrosum Dilutum. E.D. _Dilute Nitric Acid._ It is much to be regretted that the proportion of water directed for the dilution of the acid, varies considerably in the different pharmacopœias; that prepared according to the Edinburgh and Dublin formulæ, being in strength to that of the present Pharmacopœia of London, as 4 to 1: _specific gravity_, 1·080; each fluid-drachm contains nearly 8½ grains of the concentrated acid, and saturates 18 grains of crystallized sub-carbonate of soda. DOSE ♏︎x to xl. The acid is a very powerful anti-phlogistic remedy; it has been much extolled in diseases of the liver, and in syphilis. Mr. Pearson however observes that we ought not to rely upon it in any form of lues venerea, although it may be often serviceable in restraining the progress of the disease when an impaired constitution or other circumstances render the exhibition of mercury improper; when sufficiently dilute, it forms an excellent lotion for old indolent ulcers. It proves also expectorant, see _Form. 139, 140_; and it is occasionally used with success for the purpose of counteracting the consecutive effects of opium. See _Form. 16_. ACIDUM NITROSUM. E.D. _Nitrous Acid._ QUALITIES. A liquid emitting fumes of a flame-red colour, and of a very pungent and remarkable odour. The acid is either blue, green, straw-coloured, clear orange yellow, according to the proportion of nitrous acid gas[353] with which it is charged. CHEMICAL COMPOSITION. This acid is improperly denominated _Nitrous_, for it is nitric acid, holding nitrous acid gas loosely combined; by dilution this last constituent is disengaged, and the acid, after passing through a succession of different colours, becomes pure nitric acid; the application of a gentle heat effects the same changes. ACIDUM SULPHURICUM. L.E.D. Sulphuric Acid. _Oil of Vitriol, Vitriolic Acid._