An essay on combustion, with a view to a new art of dying and painting

Having treated of the effects of hydrogen gas, and sulphur, separately, I shall next treat of their effects, when combined in the form of sulphurated hydrogen gas.

I obtained this elastic fluid by pouring water, acidulated with sulphuric acid, on alkaline sulphure, prepared in the manner mentioned in the preceding chapter; but had it been prepared with a caustic alkali, it is probable, the gas would be more powerful. The sulphure of the shops is generally unfit for these experiments.

It is necessary in experiments with sulphurated hydrogen gas, hydrogen gas, &c. to have some mode of conveying them into a chimney; as they are offensive, and unwholesome.

Exp. 1. Gold

A piece of silk, which was immersed in a solution of nitro-muriate of gold in water, and dried in the air, was exposed to sulphurated hydrogen gas: the silk got a slight tinge of brown; but no other change occurred: it was then wetted with alcohol, and after some time, the brown became more intense; and white films appeared on some parts of the silk, owing to moisture collected from the gas, which is always replete with water.

Another bit of silk was dipped in the same solution of gold, and exposed, while wet, to the gas: the yellow colour, which the solution of gold gave the silk, was immediately changed to a brown; and a white metallic pellicle appeared, and covered the whole surface of the silk opposed to the gas; but no purple, or other colours, that usually attend the reduction of this metal by other agents, could be perceived. This pellicle did not entirely disappear, as the silk became dry; though it lost most of its lustre, and looked more like silver, or some other white metal imperfectly reduced, than gold.

This elastic fluid, and alkaline sulphure, have an effect on the reduction of gold, very different from that of the vapour of sulphur, obtained from a burning match, which further appears from the following experiment, made with sulphurated hydrogen gas, that happened to be mixed with some sulphurous acid gas.

Exp. 2. Gold.

A piece of silk, which was dipped in a solution of gold in ether, and dried in the air, was exposed to a current of sulphurated hydrogen gas, containing some sulphurous acid gas; but no signs of reduction could be perceived: the silk was then wetted with alcohol; still no visible change was produced, except a brown stain, where the alcohol most abounded: this stain, after some minutes exposure to atmospheric air, was covered with a white metallic film, which soon disappeared: after some minutes, the silk was wetted with water, and exposed again to the gas; a white metallic film immediately appeared, and the brown stain began to change slowly to a purple; the silk was soon covered with various colours, as blue, red, and orange; and some spots of reduced gold of its own proper colour appeared: after some time the white film, and all the colours, except the purple, disappeared: some specks of the perfectly reduced gold were permanent.

Another bit of silk, which was immersed in an aqueous solution of gold, and exposed to the same mixed gas, exhibited nearly the same appearances.

Exp. 3. Gold.

Having found that sulphurated hydrogen gas had a powerful effect in reducing other metals, I was desirous of trying its effects on a larger scale, thinking it might be attended with more success: I therefore immersed a quarter of a yard of silk in an aqueous solution of gold, and exposed it, while wet, to this gas in close vessels: the silk was soon covered with a white metallic pellicle, which disappeared in a short time: the experiment was continued about twelve hours, and, on withdrawing the silk from the gas, I could not perceive the smallest vestige of reduced metal, or purple, or other colours, that constantly attend the reduction of gold.

The silk had a dull brown hue verging on a slate colour.

Exp. 4. Silver.

A piece of silk, which was immersed in a solution of nitrate of silver in water, and dried in the air, was exposed to a current of sulphurated hydrogen gas; but no change could be perceived for some time; at length, when the silk collected moisture from the gas, some particles of reduced silver were visible, accompanied by a brown stain.

Another piece of silk was dipped in the same solution of nitrate of silver, and exposed, while wet, to the gas: the silver was instantly reduced all over the side of the silk opposed to the current: a great variety of beautiful colours, as red, orange, yellow, green, and blue, attended the reduction: most of these disappeared; but part of the silver remained permanently reduced.

I found, that, if the silk be immersed in a solution of silver in alcohol, and dried, and then moistened with water, and exposed, while wet, to the gas, none of these colours appear.

This experiment was repeated on a quarter of a yard of silk in close vessels, and immediately both sides of the silk were covered with reduced silver, attended with the same beautiful colours: the silk was left exposed to the gas seven or eight hours; and being then examined, no reduced silver could be seen: nothing remained, but a strange medley of colours, chiefly blue, green, purple, and orange, unequally mixed, some prevailing more than others in certain parts of the silk: however the die is by no means disagreeable.

Exp. 5. Silver.

A piece of silk, which was immersed in a solution of fused nitrate of silver in alcohol, and dried in the air, was exposed to a current of the gas; but no change could be perceived for some time: it was then wetted with alcohol, still no alteration could be observed, till the silk attracted moisture from the gas, when small particles of reduced silver began to appear, attended with a brown stain.

If the silk immersed in the solution of silver in alcohol, and exposed while wet to the gas, be kept constantly wet with alcohol, these appearances take place sooner.

A piece of silk, which was dipped in a solution of muriate of silver in ammonia, and exposed, while wet, to the gas, had in a short time its surface covered with reduced silver: but another piece of silk dipped in the same solution of silver, and dried, underwent no such change.

Exp. 6. Platina.

A bit of silk, which was dipped in a solution of nitro-muriate of the ore of platina in distilled water, and dried in the air, was exposed to a current of sulphurated hydrogen gas; but underwent no perceptible change.

Another bit of silk was immersed in the same solution of platina, and exposed, while wet, to the gas; the whole surface of the silk, opposed to the current, was instantly covered with reduced platina, which soon lost its lustre; nothing remaining but a brown colour, with some faint vestiges of the reduced metal.

This experiment was repeated on a bit of linen with the same result.

Exp. 7. Mercury.

A bit of silk, which was dipped in a solution of oxygenated muriate of mercury in distilled water, and dried in the air, was exposed to a current of the gas; the only visible change produced was a slight shade of yellow on part of the silk.

Another bit of silk was immersed in the same solution of mercury, and exposed, while wet, to the gas: the mercury was immediately reduced; but soon lost its lustre: the gas reacting changed most of it to a substance of a dull white colour.

The same experiments were made with nitrate of mercury, with the same result.

Exp. 8. Copper.

A bit of silk was immersed in a solution of sulphate of copper in distilled water, and suspended in the air to dry; it was then exposed to a current of the gas: the silk assumed a brown colour; but no other change appeared.

Another bit of silk was dipped in the same solution of copper, and exposed, while wet, to the gas: a white metallic film, attended with a brown stain, immediately appeared: some parts had a yellow film approaching to the colour of copper: these films all disappeared, leaving behind a brown stain: the parts, which were covered with the yellow film, resembling copper, exhibited, after some time, a dull bluish disagreeable matter.

Exp. 9. Lead.

Having dipped a piece of silk in a solution of acetite of lead in distilled water, and dried it in the air, I exposed it to a stream of the gas: the silk became a little brown; but no other change could be observed.

Another bit of silk was immersed in the same solution of lead, and exposed while wet to the gas; no sooner did it touch the silk, than a brown tinge diffused itself, like a passing shadow, over the whole surface of the silk, accompanied with a bright coat of reduced lead, which resembled silver.

The brown tinge, which the silk acquires, resembles what happens when white paper is slightly singed by holding it near a burning body.

This experiment was repeated on a quarter of a yard of silk in close vessels; and the silk was immediately covered with a coat of reduced lead, which had the brilliance of silver, and was attended with a brown tinge: the experiment was continued several hours, after which the silk was examined, and found to have lost all the argentine lustre, which was succeeded by a sparkling gray die: a sulphure of lead, or galena, being formed in the fibres of the silk. The same experiment was repeated on two other pieces of silk with the same result.

This elastic fluid is so powerful a reducer of the metals, that if chambers, painted with white lead, have any considerable degree of moisture, and are exposed to its influence, the lead on the surface of the walls is reduced, and that chiefly where the humidity is most abundant: this effect, I observed, was produced, even at the distance of three chambers from the place, where the gas was formed: and the lead was reduced most evidently behind the window-shutters where the moisture of the wall was most considerable.

It is a common experiment with chymists, in order to show the effects of this gas, to draw characters with a solution of sugar of lead on paper, which they place over a glass of water, containing some alkaline sulphure: in some time the characters drawn on the paper acquire a brown, or black colour, and become visible; which amuses the spectators.

But it is surprising, that the metal has never been reduced in this experiment even by chance; and not less so, why lead should be singled out for this trial of skill, in preference to other metals, which are equally affected by this gas.

Exp. 10. Tin.

A piece of silk was dipped in a solution of muriate of tin in distilled water, and dried in the air; the silk, on exposure to a current of the gas, scarce underwent any change, except a few brown specks dispersed over its surface.

Another bit of silk was immersed in the same solution of tin, and exposed, while wet, to the gas, which no sooner touched the silk, than the surface opposed to the current was covered with reduced tin of great brightness: in some time various colours, as blue, orange, and a faint purple, appeared, and became more evident, as the reduction proceeded.

The gas does not react on this metal so much as on mercury, and some other metals: part of the reduced tin remained permanent; but most of it disappeared, and left behind a disagreeable brown stain.

Exp. 11. Arsenic.

A bit of silk was immersed in a solution of muriate of arsenic in distilled water, and dried in the air; it was then exposed to a stream of sulphurated hydrogen gas; but no change could be observed, except a faint tinge of citron yellow, which appeared on some parts of the silk.

Another bit of silk was dipped in the same solution of arsenic, and exposed, while wet, to the gas: the arsenic was instantly reduced all over the surface, opposed to the gas, attended with a citron yellow colour.

The gas soon reacted on the reduced arsenic; and nothing remained but the yellow stain.

Exp. 12. Bismuth.

I dissolved some bismuth in nitric acid, and evaporated the solution to dryness; the salt was then dissolved in distilled water, and the solution deposited a copious white precipitate, but retained a quantity of the metal sufficient for these experiments.

In this solution of bismuth a piece of silk was immersed, and dried in the air; it was then exposed to a stream of the gas: and the only visible effect produced was a very faint tinge of brown.

Another bit of silk was dipped in the same solution of bismuth, and exposed wet to the gas: the silk was instantly covered with a bright pellicle of reduced bismuth, which soon lost most of its metallic lustre, being changed by the reaction of the gas to a sulphure.

Mr. Kirwan in his experiments on hepatic air, found, that nitrous solution of bismuth, by mixture with a solution of hepatic air in water, changes to a reddish brown, and even assumes a metallic appearance.

He also found that nitrates of silver, lead, and acetite of lead, were precipitated black.

Exp. 13. Antimony.

A piece of silk, which was immersed in a solution of tartarite of antimony in distilled water, and dried in the air, was exposed to a stream of the gas; but suffered no visible change, except that a few specks of yellow, and orange appeared.

A bit of silk was dipped in the same solution of antimony, and exposed, while wet, to the gas; the antimony was immediately reduced to its metallic form, attended with a deep orange colour: in some time, most of the metallic lustre disappeared, a few specks only remaining permanent.

Exp. 14. Iron.

A piece of silk was immersed in a diluted solution of sulphate of iron in distilled water, and dried; it was then exposed to a current of the gas; but underwent no visible change.

Another bit of silk was dipped in the same solution of iron, and exposed, while wet, to the gas: the silk soon began to acquire a dark colour, which gradually increased, and, at length, became black, attended with an obscure metallic film. The silk was immersed in water, and deposited a bright metallic film on the surface of that fluid.

Exp. 15. Zinc.

A bit of silk, which was immersed in a diluted solution of sulphate of zinc in distilled water, and dried in the air, was exposed to a current of the gas; but underwent no visible change.

Another bit of silk was dipped in the same solution of zinc, and exposed, while wet, to the gas; but no change in the colour of the silk, or sign of reduction could be perceived: the silk was then immerged in a glass of clear water, and transferred to its surface a bright metallic film of the colour of zinc.

When a languid stream of gas was employed in these experiments, the films transferred to water were scarce visible.

Exp. 16. Zinc.

A piece of silk, which was immersed in a largely diluted solution of muriate of zinc, and dried in the air, was exposed to a brisk current of sulphurated hydrogen gas; but underwent no visible alteration.

Another bit of silk was dipped in the same solution of zinc, and exposed, while wet, to the same brisk current of gas; instantly the surface of the silk, opposed to the gas, was covered with a bright coat of reduced zinc, attended with faint orange, and purple colours.

Though the reduced zinc was quite evident; yet I had the curiosity to examine its appearance on the surface of water; I therefore immersed the silk in a glass of that fluid, and a bright metallic pellicle, which retained the texture of the silk, as wax retains the impression of a seal, was transferred to its surface.

Another bit of silk, dipped in the same solution of zinc, and exposed for a longer time to the gas, lost its metallic lustre, the zinc being changed to a sulphure by the reaction of the gas.

These experiments on sulphate, and muriate of zinc, show, that the acid, in which the metal is dissolved, influences the reduction in a remarkable manner.

It is evident from the experiments related in this chapter,

1. That water is essential to the reduction of metals by sulphurated hydrogen gas.
2. That alcohol does not promote these reductions, without the aid of water.
3. That sulphurated hydrogen gas does not reduce the metals by giving them phlogiston; nor by uniting with, and separating, their oxygen: for were either of these opinions well founded; metallic solutions in alcohol should be as effectually reduced by this gas, as metallic solutions in water are.

When we consider, that alkaline sulphure reduces the metals by decomposing water; we have every reason to conclude, that sulphurated hydrogen gas reduces them in the same manner; since the same circumstances are necessary to both: the hydrure of sulphur, which constitutes the base of this gas, attracts the oxygen of the water, while the hydrogen of the latter unites, in its nascent state, with the oxygen of the metal, and reduces it.

Hence it follows, that the hydrure of sulphur is oxygenated by the oxygen of the water, while the metal is restored to its combustible state.