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.

    17/248 (page 13)
    and the seeds of some plants, are compounds of carbon, oxygen, hydrogen, and nitrogen. They possess many of the chemical properties of the mineral alkalies. Alkaline Salts should, when neutral, have neither alkaline nor acid properties; but some salts combine with two propor- tions of acid. When the acid is in excess, bi or bin is added to the appellation of the salt, as bicarbonate of potassa. They require for their solution various proportions of water, from one- half to 2,000 times the weight of the salt. When they attract moisture they are said to be deliquescent; when they lose their water of crystallization, become opaque, dry, and easily fall to powder, efflorescent; if, when exposed to heat, they gradually dry to a mass, they are said to undergo the watery fusion; and to decrepitate, if they split, fly, and crackle, when exposed to a high temperature. The salts most commonly adulterated are carbonas potassce and carbonas sodce. To try the first, make a solution of one part of the salt in eight of distilled water. If this become turbid after being neutralized with pure nitric acid, it indicates the presence of silex; if a white precipitate be thrown down in the neutralized solution by chloride of barium or acetate of lead, sulphuric salts are indicated; and hydrochloric salts by a white precipitate being formed with nitrate of silver. If a white pre- cipitate be produced by a solution of oxalate of potassa, lime, or its carbonates, are present. The same tests show the presence of similar substances in carbonate of soda, if added to a saturated solution of it in nitric acid. The addition of tartaric acid dis- covers potassa, by forming a precipitate of bitartrate of potassa. The deliquescent and efflorescent salts should be kept and dispensed in stopped bottles; while those that are persistent will not suffer from being put up in paper. EARTHS, AND THEIR SALTS. The earths, like the alkalies, are mostly compounds of oxygen with metallic bases. They are of very difficult fusibility; very sparingly soluble; and unite with the acids, forming neutral salts. Those which are soluble in water possess properties very similar to those of the alkalies; they are caustic; change to green vegetable blues and reds; and combined with oils, form soap. Two earths only in their pure state are used in medicine, namely lime and magnesia. The former, which is chiefly em- ployed in pharmaceutical operations, should be used as soon after it is burnt as possible; and each should be preserved in very closely-stopped bottles, as both attract,, powerfully, the carbonic acid contained in atmospheric air. The solution of lime or lime-water should be kept in small bottles perfectly full and well corked; for, by the contact of air, the lime attracts