FIG. 163.

phur to a temperature of from 260° to 300° C., and then suddenly cooling it by pouring it in a thin stream into water (Fig. 163). It is a dark-brown tenacious mass, which may be drawn into threads like India-rubber. It has a specific gravity of 1.95, and is insoluble in carbonic disulphide. It gradually changes to the ordinary modification. Sulphur is consumed largely in the manufacture of hydric sulphate, of gunpowder, and of friction-matches. Milk of sulphur is extensively used in medicine. The plastic modification is. often employed to take impressions of medals, coins, and similar objects.

Amorphous Sulphur.

412. Hydric Sulphide (H,S) (Sulphuretted Hydrogen). -Hydric sulphide was discovered by Scheele, in 1777. It is found abundantly in Nature as a volcanic product, as the essential ingredient to which the waters of so-called sulphur-springs owe their flavor, and as one of the bodies resulting from the decay of organic matter.

413. Preparation and Properties.—It is usually obtained by the action of dilute hydric sulphate on ferrous monosulphide.

Fe"S+H2SO=Fe”SO1+H2S

Fig. 164 represents a convenient arrangement for its evolution. The ferric monosulphide should be broken into small lumps and placed in the flask. The cork and tubes may then be adjusted, and, first, water, and then hydric sulphate poured in through the funnel-tube. The gas is absorbed by the water of the second vessel. The solution must be kept in tightly-secured bottles, as, if exposed

FIG. 164.

to the air, it is gradually decomposed. Hydric sulphide is a colorless transparent gas, having the well-known odor of rotten eggs. Cooled to 74°, or submitted to a pressure of 17 atmospheres at 10°, it condenses to a colorless mobile liquid of 0.9 specific gravity, which freezes at -85°, the frozen portion sinking in the liquid. It readily dissolves in water, imparting to the solution its taste and smell. Its reaction on vegetable colors is slightly acid, and heated in the air it burns with a pale-blue flame. When breathed it is highly poisonous, and even when much diluted with air it has proved fatal to many of the lower animals. Hydric sulphide is used extensively in chemical operations as a re-agent. Its action upon solutions of the metals may be shown by the apparatus represented in the

accompanying cut (Fig. 165). The gas is evolved from ferrous sulphide in a two-necked bottle, and passed through

a second bottle containing a little water, after which it successively passes through bottles containing solutions of cupric sulphate, zinc sulphate, ferrous sulphate, and lead sulphate. The cupric sulphate in the first bottle will give a black precipitate, that in the second a white, while the last ones yield black precipitates.

414. Chloric Disulphide, Cl,S,.-This compound, more generally termed chloride of sulphur, is obtained by passing dry chloric gas over melted sulphur. It is a deep orangeyellow liquid of peculiar disagreeable odor, boiling at 136° C. It is instantly decomposed by water. Chloric disulphide is employed in the vulcanization of caoutchouc.

415. Sulphur and Oxygen.-Sulphur may unite with oxygen as a dyad, tetrad, or hexad. The following are the oxides and acids with which we are acquainted:

416. Sulphurous Oxide, SO,.-This substance occurs among the products of volcanic action, and is always formed by the combustion of sulphur in air, or in pure oxygen, thus:

S2+0=2(SO2)

It is a transparent, colorless gas, of 2.25 specific gravity, having a pungent, suffocating odor, familiarly known in the case of a burning match. It extinguishes combustion; hence sulphur is often thrown into the fire to quench the burning soot of chimneys. It has a strong attraction for water. Allowed to escape into the air, it forms white fumes with its moisture, and a piece of ice thrust into the gas is instantly liquefied. Water at 60° F. takes up large quantities of this acid, the solution formed having the taste and smell of the gas. By cold or pressure it condenses into a liquid, of 1.49 specific gravity, which evaporates so fast that the cold generated will freeze water even in a red-hot crucible. At 76° C. it becomes solid.

417. Uses.-Sulphurous oxide is used as a disinfectant, and in bleaching woolen and straw fabrics. The goods are

FIG. 166.

moistened, and suspended in large chambers, or, in a small way, they are put into inverted barrels, and exposed to the fumes of burning sulphur. The effect is produced, not by destroying the coloring matter, as in the case of chlorine, but by the union of the acid with the coloring matter, which forms a white compound. If a red rose is held over burning sulphur, it is whitened, but the color is at once restored by weak sulphuric acid, which, being stronger, discharges sulphurous oxide from combination. The bleaching power of sulphurous oxide upon flowers may be illustrated by burning sulphur under a glass, within which are some highlycolored flowers. (Fig. 166.) If woolens, after sulphurbleaching, are washed with a strong alkaline soap, the acid is neutralized by the alkali, the coloring matter liberated, and the yellowish color restored.

418. Sulphurous Acid, Hydric Sulphite, H,SO,.—The solution of sulphurous oxide in water contains a definite compound of the form H,SO,, which is possessed of strong acid properties. It is sometimes used for the same purposes for which sulphurous oxide is employed. The hydrogen in this compound is replaceable wholly or in part by metallic elements, giving rise to numerous salts known collectively as sulphites.

419. Sulphuric Oxide, SO,.-This may be obtained in the form of a white snowy solid, by heating disulphuric acid, and collecting the fumes which pass over into a receiver surrounded by a freezing mixture. While in this

condition, it exhibits no acid properties, and may be handled with impunity, if the hands are dry. But it fumes in the air, and rapidly absorbs moisture. When thrown into

water it hisses like a hot iron, and the solution thus formed possesses all the properties of the ordinary acid.

420. Sulphuric Acid, Hydric Sulphate, H2SO,.-This important chemical compound was known as early as the fifteenth century. It is found native in a dilute condition, in volcanic regions, and in the waters of some springs and rivers. Sulphuric acid may be prepared on a small scale

FIG. 167.

a

Preparation of Sulphuric Acid.

in an apparatus represented by Fig. 167. A large glass balloon, a, is connected by tubes with three flasks. Flask > supplies it with sulphurous oxide; c, with nitric dioxide; d, with steam, and the short tube furnishes air. These four substances re

FIG. 168.

the manufactory the

balloon is represent

Liberating Sulphuric Acid.

ed by large chambers lined with sheet-lead, and the flasks by furnaces (Fig. 168). In one furnace sulphur is heated,