The liquid known as hydrochloric or muriatic acid, or spirit of salts, is an aqueous solution of the pure muriatic acid, which is a colourless, invisible gas possessing a pungent odour and an acid taste, and fuming when in contact with the atmosphere. This gas is irrespirable, uninflammable, has a specific gravity of 1.2695, and becomes liquid under a pressure of forty atmospheres. Muriates or hydrochlorates are combinations of this gas with a base. One method of producing the liquid ordinarily known as muriatic acid is to slowly pour 11 fl. oz. of sulphuric acid into 8 fl. oz. of water, and, when cold, add to 12 avoirdupois oz. of dried chloride of sodium contained in a quart flask; through a cork in the neck of the latter passes a glass tube which is connected with a three-necked wash-bottle, furnished with a safety tube, and containing 1 oz. of water. Heat the contents of the flask, conduct the disengaged gases to the wash-bottle, and thence, by means of a glass tube, to a bottle containing 12 1/2 fl. oz. of distilled water; in this bottle the tube dips 1/2 in. below the surface. Con-timie the process until 16 1/2 fl. oz. of muriatic acid are obtained. The last bottle must be kept cold during the operation.
Commercial hydrochloric acid is a secondary product of the manufacture of carbonate of soda.