Thomson's Conspectus of the British pharmacopoeias.

  • Thomson, Anthony Todd, 1778-1849.
Date:
1852
Catalogue details

Licence: Public Domain Mark

Credit: Thomson's Conspectus of the British pharmacopoeias. Source: Wellcome Collection.

    16/248 (page 12)
    The stronger acids should be kept in well-stopped glass bottles, and the name of the acid each bottle contains engravei on the glass. They should also be dispensed in glass-stopped phials; for cork blackens the sulphuric acid, and it is dissolved by the nitric and the hydrochloric acids. Sulphuric acid is sometimes adulterated with sulphate of potassa; which may be detected by saturating the acid with ammonia, and exposing it in a crucible to a red heat, so as to expel the sulphate of ammonia;—the sulphate of potassa, when present, will remain in the crucible. Nitric acid, also, is sometimes adulterated with sulphuric and hydrochloric acids. These adulterations are discovered by dropping into the nitric acid diluted a solution of nitrate of baryta, which is precipitated white, if sulphuric acid be present; and with a solution of nitrate of silver, the precipitation of a chloride of silver shows the presence of hydrochloric acid. In the same manner sulphuric acid is detected in acetic acid, by dropping into it a solution of acetate of baryta; copper by the acid becoming bluish when supersaturated with ammonia; or the ferrocyanate of potassa throwing down a copper-coloured precipitate; and lead, by a black precipitate being thrown down when sulphuretted hydrogen gas is added to it. ALKALIES, AND THEIR SALTS. Two of the mineral alkalies employed in Pharmacy are compounds of oxygen with metallic bases; ammonia is a compound of hydrogen and nitrogen. They possess properties the reverse of the acids. Their taste is urinous and acrid: they change to green or blue, the vegetable red colours: they are caustic, or inflame and corrode the skin, and dissolve animal matter: they have a strong affinity for water, and by their greater solubility in it are distinguished from the earths; they unite with oils and fat, forming soap; and form neutral salts with the acids. There are three alkalies: one is volatile, and cannot be obtained per- fectly pure in a solid form; the other two are fixed. They should be kept in well-stopped glass bottles, and dispensed in glass-stopped phials. Ammonia, the volatile alkali, is often over diluted with water, which may be known by the spec. grav. of the fluid: or a phial capable of containing 224 grains of distilled water should hold 216 grains of liquor ammoniae. Liquor potassce often contains lime, which is known by the solution, diluted with distilled water, becoming milky when the breath is blown through it; or on a solution of carbonate of potassa being added to it; the lime being thus formed into a carbonate. The purity of potassa, in the solid form, is of little consequence, as it is used for ex- ternal application only : pure soda is not used in medicine. The Alkaloids, or alkalies found in the barks, and the leaves,