Prep. By the action of sulphuric acid in excess upon nitrate of potash in a glass retort, when nitric acid and bisulphate of potash are formed; the former, being volatile, distils over.

Prop. & Comp. A colourless transparent liquid, with a strongly acrid odour, and intensely acid taste; sp. gr. 1.50; [1.420, U. S.] it fumes in the air, and entirely volatilizes with heat. Composition (3 HO, 2 No5). When diluted with three times its volume of water and poured upon copper it gives off a colourless gas, which, upon contact with air, becomes an orange vapour, and when conducted into a solution of sulphate of iron, communicates to it a dark colour. When diluted with six parts of water, it gives no precipitate, either with nitrate of silver, or chloride of barium. One fluid drachm of the acid requires for neutralization 121.5 measures of the volumetric solution of soda, indicating that not more than 1 1/2 equivalent of water is present.

Off. Prep. Acidum Nitricum Dilutum. Dilute Nitric Acid. (Nitric acid, two fluid ounces; distilled water, thirteen fluid ounces.) [Nitric acid, three troy ounces; distilled sufficient to make the diluted acid measure a pint; sp. gr. 1.068. U. S.]

Colourless; sp. gr. 1.101. Six fluid drachms require for neutralization one hundred measures of the volumetric solution of soda, indicating the presence of fifty-four grains of anhydrous nitric acid (No5).