This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
An-anhydride (not a true acid), obtained by roasting arsenical ores, and purified by sublimation.
Characters. - Occurs in sublimed masses which usually present a stratified appearance caused by the existence of separate layers differing from each other in degrees of opacity, or as a heavy white powder. When slowly sublimed in a glass tube it forms minute brilliant and transparent octahedral crystals.
Solubility. - It is sparingly soluble in water.
Reactions. - Its solution gives with ammonio-nitrate of silver a canary-yellow precipitate insoluble in water, but readily dissolved by ammonia and by nitric acid. Sprinkled on a red-hot coal it emits a garlicky odour.
Impurities. - Gypsum and chalk.
Test. - It is entirely volatilised at a temperature not exceeding 400° F. Four grains of it dissolved in boiling water with eight grains of bicarbonate of sodium discharge the colour of 808 grain-measures of the volumetric solution of iodine. As2O3 + 2H2O + 4I = As2O5 + 4HI.
Dose.- 1/60 to 1/12 of a grain, in solution. It may also be given in the so-called 'Asiatic pills,' which are used in some parts of the Continent. These consist of arsenious acid, 0.75 grm., powdered black pepper, 6 grm., gum arabic, 1.5 grm., powdered marsh-mallow root, 2 grammes, to make 100 pills, of which three are to be taken daily..
B.P. | Dose. |
Liquor Arsenicalis .............................................................. | 2 8 min. |
" Arsenici Hydrochloricus ............................... | 2-8 min. |
U.S.P. | |
Liquor Potassii Arsenitis .................................................. | 2- 8 min. |
Liquor Acidi Arseniosi .................................................. | 5 min. |
Preparations of Arsenic Acid.
b. And U.S.P.
Liquor Sodii Arseniatis.
 
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