LIQUID HYDROCHLORIC ACID.

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2. Liquid Hydrochloric Acid.

Fig. 40.

Synonymes. —This is an aqueous solution of hydrochloric acid, and isusually called, for brevity, hydrochloric or muriatic acid. It is the acidumhydrochloricum of the London Pharmacopoeia.

Preparation. —(a.) According to the Pharmacopoeias. In the London Pharmacopoeia this acid is prepared by adding twenty ounces of sulphuricacid mixed with twelve fluid ounces of distilled water, to two pounds ofdried chloride of sodium, placed in a glass retort. Twelve fluid ouncesof distilled water are to be put into the receiver Distil by a sand bath.In the Dublin Pharmacopoeia a somewhat larger quantity of water isemployed. The Edinburgh Pharmacopoeia orders equal weights of sul-phuric acid, water, and chloride of sodium (previously heated to redness).

(6.) In commerce .—Manufacturers of hydrochloric acid generally em-ploy an iron orstoneware potset in brickworkover afire-place,with a stone-ware head lutedto it, and con-nected with arow of double-necked bottles,made of thesame material,and furnishedwith stop-cocks

. , . ,, • A ■, of earthenware.

Apparatus for making Hydrochloric Acid . The last bottle

is supplied with a safety tube, dipping into a vessel of water (fig. 40).

Since the manufacture of carbonate of soda from the sulphate of soda,and the consequent necessity of obtaining the latter salt in large quan- Ntities, another mode of making hydrochloric acid has been adopted Itconsists in using a semi-cylindrical vessel for the retort: the upper or flatsurface of which is made of stone, while the curved portion exposed tothe fire is formed of iron. The chloride of sodium is introduced at oneend, which is then closed by an iron plate, perforated to allow theintroduction of the leg of a curved leaden funnel, through which strongsulphuric acid is poured. The funnel is then removed, and the apertureclosed. Heat being applied, the hydrochloric acid gas is developed, andis conveyed by a pipe into a double-necked stoneware bottle, half filledwith water, and connected with a row of similar bottles, likewise contain-ing water. The gas dissolves in the water, which, when saturated, con-stitutes the common yellow hydrochloric acid of commerce, which iscoloured by iron. By a second distillation, at a low heat, a liquid nearlycolourless is obtained, which is sold as pure hydrochloric acid.

The theory of the above process is precisely that already explainedin the manufacture of hydrochloric acid gas. The salt is dried, toexpel any water which may be mechanically lodged between theplates of the crystal, and to obtain uniform weights. The Edinburgh