410

ELEMENTS OF MATERIA MEDIOA.

tion, the symptoms were those of local irritation, with vonüting and purging ofblood. The patient recovered. (Land. Med. Gaz. vol. xxv. p. 944.)

8. ÜNGIMTUM ACIM SÜLPMRICI, D. Sulphuric Aeid Ointment —(Sulphuric

Acid, 3j.; Prepared Hog's Lard, 3j. Mix.) The irigredients should be mixed ina glass or earthenware mortar. The precise changes which sulphuric acid effectson lard have not been studied : they are most likely analogous to those efFectedby the acid on olive oil. The sulphuric acid probably unites on the one hand withthe glycerine (oxide ofglycerule) of the lard to form bisulphate of glycerine,—andon the other with the fatty acids (oleic, margarie (?) and stearic acids) of the lard.This ointment is of a bufF colour. It is a powerful stimulant, and has been em-pioyed in paralysis, hemorrhages, and Scabies, as before mentioned (see p. 408.)

3. A'CIDUM SULPHURO'SUM.—SULPHUROUS ACIP.

History. —Homer (Iliad, xvi.) mentions sulphur fumigations. Stahl, Scheele,and Priestley, were the first to submit this acid to "an accurate examination. Ithas been termed Fol utile Sulphurous Acid, and, from the old mode of procuringit, Spiril of Sulphur by the Bell (Spiritus Sulphuris per Campanan.)

Natural History.— It escapes from the earth in a gaseous form, in the neigh-bourhood of volcanoes.

Preparatiox. —For chemical purposes it is prepared by mixing two parts ofmercury with three parts of strong sulphuric acid, applying heat, and collectingover mercury. The results are, the bipersulphate of mercury and sulphurousacid.

For medicinal purposes, however, it is rarely, if ever, necessary to procure it inthis way. By the combustion of sulphur in atmospheric air this gas is readily ob-tained; and when we are about to employ it, either as a disinfectant or vapourbath, this method is always followed.

Properties. —At ordinary temperatures and pressures it is a colourless andtransparent gas, and has a remarkable and well-known odour. It is neither com-bustible nor a supporter of combustion. It reddens litmus and bleaches somecolouring matters, especially infusion of roses, but the colour is restored by sulphu-ric acid. It is irrespirable, and has a sp. gr. of 2-2. It readily dissolves in water:recently boiled water takes up 33 times its volumeof this gas. By cold and pres-sure it is readily Condensed into a liquid.

Charaeteristics. —This acid is readily known by its peculiar odour (thatof burn-ing sulphur.) If the puce-coloured or binoxide of lead be added to it, the whiteprotosuiphate of lead is formed. An aqueous Solution of this acid mixed with iodicacid, deoxidizes the latter, and sets iodine free, which may be recognised by itsproducing a blue colour with starch. A Solution of an alkaline sulphate causes,with a soluble salt of barium, a white precipitate {sulphate ofbaryta.)

Constituents.

ResultingCompound.

The sulphites evolve sulphurous acid by the action ofstrong sulphuric acid.

Composition. —If 16 parts by weight of sulphur beburned in one volume or 16 parts (by weight) of oxy-gen gas, we obtain one volume or 32 parts (by weight)of sulphurous acid gas.The composition of this substance, may, therefore, be tlius expressed :—

Mtoms.

Eq. Wt.

Per Cent.

Berzelius,

Physiolooical Effects. «.. On Vegetables. —It is a most powerful poison toplants, even in very minute quantities. (Christison, On Poisons, 3d ed. p, 750.)