(e) Water, saturated with this gas, reddens the infusion of violets, in this respect producing the effect of an acid. From this and other properties, some of the German chemists have proposed for it the name of hydrothionic acid; and Gay Lussac has given it the very objectionable name of hydro-sulphuric acid, a term which would be much more properly applied to liquid sulphuric acid.

(f) Water impregnated with sulphureted hydrogen, when exposed to the atmosphere, becomes covered with a pellicle of sulphur. Sulphur is even deposited when the water is kept in wellclosed bottles.

(g) On the addition of a few drops of nitric or nitrous acid to the watery solution, sulphur is instantly precipitated. In this case the oxygen of the acid combines with the hydrogen of the gas, and the sulphur is separated. The gas itself, also, is decomposed when transmitted through sulphuric, nitric, or arsenic acids.*

(h) This gas, as will afterwards appear, is decomposed by mixture with oxy-muriatic acid gas; and sulphur is precipitated. Vogel obtained, also, a liquid, analogous to the sulphureted muriatic acid of Dr. Thomson.

(i) It is decomposed also when kept in a state of mixture with atmospheric air, the oxygen of which combines with the hydrogen, and forms water, while the sulphur is precipitated.

(k) A succession of electric explosions throws down sulphur from it, and the volume of the gas remains unaltered.

(1) When six measures of sulphureted hydrogen gas and five measures of sulphurous acid gas are mingled together, the hydrogen of the former unites with the oxygen of the latter, and the sulphur of both is precipitated. But five measures of sulphurous acid contain twice the oxygen necessary for saturating six measures of sulphureted hydrogen. Hence it is probable, that the sulphur is separated in the state of an oxide.

(m) It is decomposed when passed over ignited charcoal, and is converted into carbureted hydrogen gas.

(n) Sulphureted hydrogen, both in the state of a gas and of watery impregnation, precipitates all metallic solutions, excepting those of iron, nickel, cobalt, manganese, titanium, and molybdena. (0) It is copiously absorbed by alkalies, and by all the earths, excepting alumine and zircon. These alkaline and earthy combinations are termed hydro-sulphurets.

(p) When potassium or sodium is made to act on sulphureted hydrogen gas, a brilliant combustion takes place; a quantity of hydrogen gas is evolved, precisely equivalent to that which the metal would have separated from water; the metal loses its lustre, and becomes grayish, or amber coloured, or reddish; and by the action of diluted muriatic acid, the whole of the sulphureted hydrogen, is recovered. This experiment proves, that sulphureted hydrogen, and consequently sulphur, contain no oxygen; for, in that case, the potassium would not, after being acted on by the gas, evolve the original quantity of sulphureted hydrogen. All that appears

* Journal of Science, &c. ii. 152.

to take place is, the combination of the metal with sulphur, and the formation of a sulphuret of potassium or sodium, which disengages from water exactly as much hydrogen, as would have been evolved by the metal in its separate state. The results of Sir H. Davy, which are somewhat different, are satisfactorily explained by Gay Lussac and Thenard.*

(4) The specific gravity of sulphureted hydrogen gas has been variously stated. Mr. Kirwan found 100 cubic inches, at 60° Fahrenheit, and 30 inches barometer, to weigh 34.286 grains, which makes its specific gravity 1.124. Sir H. Davy states the weight of the same quantity at 36.5 grains, and its specific gravity, therefore, at 1.180. Gay Lussac and Thenard determined its specific gravity to be 1.1912 by experiment, or 1.1768 by calculation; and 100 cubic inches should weigh 36.33 grains, according to the first of these two numbers.

(r) Admitting the accuracy of Sir H. Davy's statement of its specific gravity, and also that 100 cubic inches of the gas contain exactly the same volume of hydrogen (= 2.27 grains), then 36.5 grains of sulphureted hydrogen will contain 2.27 grains of hydrogen; and 100 grains will consist of

From these data, which agree very nearly with those of Berzelius, the weight of the atom of sulphur may be stated at 15; for as 6.2 to 93.8 so is 1 to 15 very nearly. The weight of this atom, therefore, turns out to be the same, whether investigated by its combinations with oxygen or with hydrogen.

ART. 3.-Hydro-Sulphurets.

In its union with alkaline and earthy bases, sulphureted hydrogen seems to perform, in a great measure, the functions of an acid; and presents, therefore, an important exception to the doctrine of acidification proposed by Lavoisier; for, in this instance, a body, which contains no oxygen, possesses some of the most important characters of an acid, viz. the property of changing vegetable blues to red, and of uniting with alkalies.

I. The hydro-sulphurets may be formed, by transmitting sulphureted hydrogen gas, as it issues from the materials that afford it, through a solution of the alkaline or earthy base. Or the base, when insoluble, must be kept suspended in water by mechanical agitation.

II. The hydro-sulphurets have several qualities common to the whole genus.

1. They are all soluble in water, and the recent solution is colourless. By exposure to the air however, it first becomes green, +81 Ann. de Chim. 26.

* Recherches, i. 202.

or greenish yellow, and deposits sulphur on the sides of the vessel. The glass bottle, containing the solution, becomes black on its inner surface, in consequence of the combination of sulphur with the oxide of lead contained in the glass.

2. The solution of hydro-sulphuret of magnesia is decomposed by heat; that of lime nearly so; but those of potash and soda, though rendered much more alkaline by heat, still contain a large proportion of sulphureted hydrogen.

3. After long exposure to the atmosphere, the solution entirely loses its colour, and again becomes perfectly limpid. When examined, it is found to consist of a combination of sulphuric acid with the peculiar base of the hydro-sulphuret. This is owing to the absorption of oxygen, which all hydro-sulphurets take from the atmosphere; the formation of a sulphite; and the conversion of this, by farther oxygenation, into a sulphate. Hence, when confined in contact with a limited quantity of atmospherical air, hydro-sulphurets effect a diminution of volume; and may be employed to ascertain its proportion of oxygen. They entirely absorb pure oxygen gas.

4. When a hydro-sulphuret, fully charged with gas, is heated with sulphur, a strong effervescence ensues; much of the sulphur is dissolved; and sulphureted hydrogen escapes. If the hydrosulphuret is not fully saturated, sulphur is still dissolved, but without any escape of sulphureted hydrogen.

5. When an acid is poured on any of the hydro-sulphurets, the sulphureted hydrogen gas is disengaged and no sulphur is deposited. This non-precipitation of sulphur distinguishes hydro-sulphurets, both from sulphurets and hydrogureted sulphurets. The acid employed should be one which strongly retains its oxygen, such as the sulphuric or muriatic; otherwise it will be decomposed. A hydro-sulphuret, which has been a few days exposed to the air, yields, by this treatment, sulphurous acid gas, along with sulphureted hydrogen.

6. The solutions of hydro-sulphurets precipitate all metallic solutions. They also precipitate alumine and zircon from their solutions, but no other earths.

7. The hydro-sulphurets are, for the most part, susceptible of a regularly crystallized form.

HYDRO-SULPHURET OF POTASH forms large transparent crystals not unlike in size those of sulphate of soda, but having the shape of four-sided prisms, acuminated with four planes; or of six-sided prisms, acuminated by six planes. It is deliquescent, and affords a thick syrupy liquor, which gives a green colour to the skin. It dissolves readily in water and alcohol, producing cold. When dilute acids are added to the solution, a brisk effervescence is excited, but no sulphur is deposited. Vauquelin found that its solution in water may be evaporated to dryness, without decomposing the hydro-sulphuret; for on heating the residuum, mixed with sulphur, in a retort, sulphureted hydrogen gas was disengaged abundantly

HYDRO-SULPHURET OF SODA is a compound, which derives some importance from its being produced along with carbonate of soda, in several processes for decomposing the sulphate of soda.* It is transparent at first, colourless, and crystallized in four-sided prisms, acuminated by four planes. It has an acrid and alkaline taste, which soon becomes very bitter. Its solution is colourless, but tinges the skin or paper green. It effervesces briskly with acids, and no sulphur is deposited unless the nitric or oxymuriatic acids are added, which attract the hydrogen, and throw down sulphur.

Vauquelin has proposed to distinguish these two sulphurets, which so closely resemble each other, by the following test. The hydro-sulphuret of potash, when added to a solution of sulphate of alumine, occasions a crystallization of alum; but that of soda has no such action.

HYDRO-SULPHURET OF AMMONIA may be formed by the direct mixture of sulphureted hydrogen and ammoniacal gases in a dry vessel, cooled externally by ice. It is deposited in needle-shaped crystals. But, for all practical uses, it is better prepared, by putting a solution of pure ammonia into the middle vessel of a Nooth's machine, and passing through it streams of sulphureted hydrogen gas, till the liquid acquires a yellowish colour. In this state it constitutes the hepatized ammonia, so strongly recommended by Dr. Rollo as a remedy for diabetes.

HYDRO-SULPHURETS OF BARYTES AND STRONTITES are crystallized salts, having a white silky lustre, and readily soluble in water.t HYDRO-SULPHURET OF LIME, formed by transmitting sulphureted hydrogen through water, in which lime is kept mechanically suspended, composes a crystallizable salt, soluble in water; and having the general properties of hydro-sulphurets.‡

ART. 4.-Super-Sulphureted Hydrogen, and Hydrogureted Sulphurets.

I. Super-sulphureted hydrogen is obtained, when hydro-sulphuret of potash is poured, by little and little, into muriatic acid. A very small portion only of gas escapes; and while the greater part of the sulphur separates, one portion of it combines with the sulphureted hydrogen; assumes the appearance of an oil; and is deposited at the bottom of the vessel. Or, dissolve sulphur in a boiling solution of pure potash; and, into a phial containing about onethird its capacity of muriatic acid, of the specific gravity 1.07, pour about an equal bulk of the liquid hepar. Cork the phial, and shake it; the hydrogureted sulphur gradually settles to the bottom in the form of a brown, viscid, semifluid mass. Its properties are the following:

* Annales de Chimie, Ixiv. 59.

† Ibid. lxii. 181.

This account differs in some respects from that of Vauquelin, Ann. de Chim. et Phys. vi. 37.

1. If gently heated, sulphureted hydrogen gas exhales from it; the super-sulphuret loses its fluidity; and a residue is left, consisting merely of sulphur.

2. It combines with alkalies and earths; and forms with them a class of substances called hydrogureted sulphurets.

3. It is constituted, according to Mr. Dalton, of two atoms of sulphur, weighing 30, with one atom of hydrogen, and consists, therefore, per cent. of

There are, therefore, three distinct combinations of sulphur and its compounds with alkalies and earths. The first consist, simply, of sulphur, united with an alkaline or earthy base, and are properly called sulphurets. The second are composed of sulphureted hydrogen, united with a base, and are called hydro-sulphurets. The third contain super-sulphureted hydrogen, attached to a base, and constitute hydrogureted sulphurets.

The pure sulphurets can exist, as such, only in a dry state; for the moment they begin to dissolve in water, a decomposition of that fluid commences; sulphureted hydrogen is formed; and of this a part is disengaged, while another part, uniting with an additional proportion of sulphur, composes super-sulphureted hydrogen. This last, uniting with the base, forms an hydrogureted sulphuret. At the same time, it has been stated by Berthollet,* sulphuric acid is composed, by the action of the sulphur on the oxygen of the water. This however, Gay Lussac has shown, takes place only when the sulphuret has been formed at an unnecessary degree of heat, and that when carefully prepared at a heat below redness, the solution of an alkaline sulphuret in water contains sulphurous and hypo-sulphurous acids, but no sulphuric acid.t The sulphurets, also, being partly changed, by solution, into hydrogureted sulphurets, the effusion of an acid throws down a quantity of sulphur. A distinguishing character, also, of solutions of this kind, is that sulphur is precipitated by passing through them sulphureted hydrogen gas.

According to Proust, if red oxide of mercury be added to solutions of the kind which have just been described, the sulphureted hydrogen is removed, and what remains is a pure liquid sulphuret, from which acids precipitate sulphur only, without any effervescence.

II. The hydrogureted sulphurets are also formed by boiling ng with a sufficient quantity of water, the alkaline, or earthy e, with flowers of sulphur. Thus a solution of pure potash, e soda, or of barytes or strontites, may be changed into an hyureted sulphuret. To prepare this compound, with base of the powdered earth, mixed with sulphur, may be boiled with

de Chim. xxv. 239, 269. +6 Ann. de Chim. et Phys. 322.