rxm in.

Metallic Preparations. — Arsenic.

651

process is superflous; and as it is also not devoid of risk tothe operator, it should be altogether rejected.

LIQUOR ARSENICALIS', Lond. Arsenical Solution.

" Take of prepared oxide .of arsenic rubbed to a very finepowder, subcarbonate of potass from tartar, of each sixty-fourgrains ; distilled water, a -pint. Boil them together in a glassvessel until the arsenic be entirely dissolved. Add to thesolution when it is cold compound spirit of lavender, four fluiddrachms : and then as much distilled water as will make thewhole up to a pint."

Solutio Arsenicalis, Edin. Solution of Arsenic.

" Take of oxide of arsenic rubbed to very fine powder, verypure subcarbonate of potass, of each sixty-four grains; distilled■water fourteen ounces. Boil them together in a glass vesseluntil all the oxide be dissolved. Add to the solution, when itis cold, half an ounce of compound spirit of lavender, and asmuch distilled water as will make the whole up to sixteenounces.

The white oxide of arsenic possesses properties in somerespect similar to those of an acid. It combines with alkalies,is soluble in water, and the solution reddens tincture of litmus:but it also combines with and neutralizes the acids; so that,while some 2 regard it as an acid, others 3 consider it only as ahighly oxidized oxide. In the above process, by combinationwith die potass, its solubility is much increased, and a solutionobtained of an uniform strength, by which very minute dosescan be correctly and easily apportioned. It was introduced byDr. Fowler of Stafford, whose formula the London college hasadopted, altering only the proportions of the water and thespirit of lavender, to make up the pint of the solution.

Qualities. — This solution, one fluid drachm of which con-tains half a grain of oxide of arsenic, has the odour, taste, andcolour of the compound spirit of lavender. It is decomposedby lime-water, hydrosulphuret of potass, nitrate of silver, thesalts of copper, and instantly forms a copious precipitate whendropped into infusion or decoction of cinchona bark; withwhich, therefore, it ought not to be conjoined in extemporane-ous prescriptions.

Medical properties and uses. — The arsenical solution, as itis termed, is a powerful tonic, useful in all the cases in whichthe white oxide can be employed. (See Arsenici Oxydum, Partii.) It was introduced by Dr. Fowler as a substitute for the

1 This appellation is certainly very objectionable, as it conveys an erroneomidea of the preparation, even admitting that the term arsenic may be used todesignate the white oxide.- it should have been Liquor Arsenialis Potasstv, orperhaps more properly, Liquor alcalinus Oxidi Arsenici-

2 Fourcroy. 3 Berthollet.