Arsenici Oxydum Album Sublimatum. Dub. Sublimed White Oxide of Arsenic

"Rub the oxide of arsenic to a coarse powder, and expose it to heat in a proper vessel, guarding against the vapours, that the white oxide of arsenic may sublime."

Syn. Oxide d'arsenique pure (F.), Weisses Arsenick ( G.), Arsenico bianco (I.).

The greater part of the arsenious acid found in the shops, is in the form of semivitreous cakes, which are the product of a second sublimation of the acid after it is obtained from roasting ores of cobalt. Although prepared on a great scale, yet it is as pure as sublimation can make it, and therefore this process is superfluous, and has been properly rejected by the London College: it is also not devoid of risk to the operator.

Liquor Potassae Arsenitis. Lond. Liquor ar-senicalis, Dub. Solution of Arsenite of Potassa

"Take of arsenious acid, broken to pieces; carbonate of potassa, of each eighty grains; compound tincture of lavender, five fluid drachms; distilled water, a pint. Boil the arsenious acid and the potassa with half a pint of the water in a glass vessel until they are dissolved. Add to the solution, when it is cold, the compound spirit of lavender, and finally, as much distilled water as will make the whole accurately up to a pint."

Solutio Arsenicalis, Edin. Solution of Arsenic.

"Take of oxide of arsenic, rubbed to a very fine powder, very pure subcarbonate of potassa, of each sixty four grains; distilled water, fourteen ounces. Boil them together in a glass vessel until all the oxide be dissolved. Add to the solution, when it is cold, half an ounce of compound spirit of lavender, and as much distilled water as will make the whole up to sixteen ounces."

The arsenious acid combines readily with alkalies, forming salts very soluble in water. In the above process, by its combination with the potassa, the carbonic acid is driven off, and a solution is obtained of an uniform strength, by which very minute doses can be correctly and easily apportioned. It was introduced by Dr. Fowler, of Stafford, whose formula the London College has adopted, altering only the proportions of the water and the spirit of lavender, to make up the pint of the solution. The acid employed should be perfectly pure; the best test of which is its complete volatilisation when heated.

Qualities. - This solution has the odour, taste, and colour of the compound spirit of lavender. It is decomposed by lime-water, chloride of calcium, hydrosulphurets, sulphate of magnesia, alum, sulphate of iron, nitrate of silver, and the salts of copper; and instantly forms a copious precipitate when dropped into infusion or decoction of cinchona bark; with which therefore it ought not to be conjoined in extemporaneous prescriptions.

Medical properties and uses. - The arsenical solution, as it is termed, is a powerful tonic and anti-periodic, useful in all the cases in which the acid can be employed. It was introduced by Dr. Fowler as a substitute for the celebrated empirical remedy known under the name of "The Ague Drop," which owes its efficacy to the arsenious acid. In addition to the account we have already given of the medicinal use of this acid, we have to add, that we have given this solution with decided advantage after cupping and purging, in threatened apoplexy, when the strength was little and the complexion pale. The dose is iv. gradually increased to xxx., given twice a day.