Dr. Pereira's Elements of materia medica and therapeutics : abridged and adapted for the use of medical and pharmaceutical practitioners and students and comprising all the medicines of the British Pharmacopœia, with such others as are frequently ordered in prescriptions or required by the physician / edited by Robert Bentley and Theophilus Redwood ; with an appendix.

  • Jonathan Pereira
Date:
1874
Catalogue details

Licence: Public Domain Mark

Credit: Dr. Pereira's Elements of materia medica and therapeutics : abridged and adapted for the use of medical and pharmaceutical practitioners and students and comprising all the medicines of the British Pharmacopœia, with such others as are frequently ordered in prescriptions or required by the physician / edited by Robert Bentley and Theophilus Redwood ; with an appendix. Source: Wellcome Collection.

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    gallon. Connect the flask by corks and a bent glass tube with a three-necked bottle, furnished with a safety tube, and containing the remaining four ounces of the water ; then, applying heat to the flask, conduct the disengaged gas through the wash-bottle into a second bottle containing the distilled water, by means of a bent tube dipping about half an inch below its surface ; and let the process be con- tinued, until the product measures sixty-eight ounces, or the liquid has acquired a specific gravity of 116. The bottle containing the distilled water must be kept cool during the whole operation.] In the above operation, the proportions of acid and salt are, ac- cording to the formula, NaCl + H2S04 = NaHS04+ HC1. These proportions are employed for two reasons: 1st, a much lower heat is required : and, 2ndly, the resulting salt, bisulphate of soda, is easily got out without risking the flask, which is not the case when double the amount of salt is used, and neutral sulphate is left. The addition of the water facilitates the operation, and renders the re- sulting mass more soluble and manageable. [§ Characters and Tests.—A colourless and strongly acid liquid, emitting white vapours having a pungent odour. Specific gravity 1*16. When evaporated to dryness it leaves no residue. It gives with nitrate of silver a curdy white precipitate soluble in excess of ammonia, insoluble in nitric acid. 1148 grains mixed with half an ounce of distilled water require for neutralisation 1,000 grain- measures of the volumetric solution of soda. When diluted with four times its volume of distilled water, it gives no precipitate with solution of chloride of barium, or sulphuretted hydrogen, and does not tarnish or alter the colour of bright copper foil when boiled with it. If a fluid drachm of it mixed with half an ounce of distilled water be put into a small flask with a few pieces of granulated zinc, and while the effervescence continues a slip of bibulous paper wetted with solution of sub-acetate of lead be suspended in the upper part of the flask above the liquid for about five minutes, the paper will not become discoloured.] The tests prove absence of fixed impurity, of sulphuric acid, free chlorine, lead, arsenic, and sulphurous acid. Properties.—Pure liquid hydrochloric acid, possesses the usual characteristics of a strong acid ; is decomposed by some metals (e.g. zinc and iron), hydrogen being evolved, and a metallic chloride formed. When it acts on a metallic oxide, water and a metallic chloride are produced. It is without action on gold leaf, and does not decolorise sulphate of indigo. A rod dipped in a solution of caustic ammonia produces white fumes when brought near strong liquid hydrochloric acid. Commercial hydrochloric acid is frequently more or less impure, being contaminated with iron, sulphuric and sulphurous acids, chlorine, arsenic, chloride of ammonium, &c.