The finest effect is produced when the flashes of gas succeed each other but slowly.

RATIONALE.... We have noticed before that phosphorated hydrogen gas is nothing but hydrogen gas holding phosphorus in solution. When this gaseous fluid is presented to the atmospheric air or oxygen gas, the minutelydivided phosphorus rapidly attracts oxygen and kindles, setting fire at the same time to the hydrogen gas in contact with atmospheric air, and hence phosphoric acid and water are formed.

The circular crown of white smoke which rises after the explosion of the gas, originates from the coat of water which enveloped the bubble of the gas; this water, together with what is formed during the explosion, is suddenly converted into vapour, it unites to the phosphoric acid produced, and thus constitutes the circular crown of smoke which rises like a ring.

If a wide mouthed phial be filled with phosphorated hydrogen gas and left in that situation over mercury, the gas will take fire when suffered to escape into the air by inclining the phial.

REMARK....This last is a hazardous experiment: the phial is often burst to pieces; it is therefore necessary to surround it with a cloth, in order to avoid dangerous events. An elastic gum bottle may be used for this purpose with safety.*

EXPERIMENT II.

Accension of phosphorated hydrogen gas by means of

oxygen gas.

Fill a receiver with oxygen gas, and convey into it a few bubbles of phosphorated hydrogen gas. At the instant of the union of the gases, a brilliant flash of fire takes place, accompanied with a report.

The rationale of this experiment is analogous to the former.

REMARK.... Great caution is necessary in performing this experiment. The dilatation of the gases which takes place during the explosion is so great that the vessel is apt to be blown to pieces. Not more than a single small bubble of the phosphorated hydrogen gas should be con

* Invert a tin case over the phial before you let out the gas. T. C.

veyed into the oxygen gas at once, except the receiver be made of very thick glass.

EXPERIMENT III.

Accension of phosphorated hydrogen gas, by means of oxygenized muriatic acid gas.

If fresh-prepared phosphorated hydrogen gas and oxygenized muriatic acid gas are mingled together over mercury, a considerable detonation takes place, accompanied with a lambent flame and dense white vapour. green RATIONALE.... All that happened in the last experiments takes place in this instance. The oxygenized muriatic acid is robbed of its oxygen, and becomes converted into simple muriatic acid gas; and water and phosphoric acid are produced. The evolved heat inflames the phosphorus which was dissolved in the gas.

REMARK.... For the success of this experiment it is essential that both gases are fresh prepared. The receiver in which the mixture is made should be very strong, in order to guard against accidents, and the gas introduced gradually by a bubble at a time.

EXPERIMENT IV.

Phosphorated hydrogen gas burns with a green light in nascent oxygenized muriatic acid gas, under

the surface of water.

Put into an ale-glass, or Florence flask, one part of phosphuret of lime, broken into pieces of the size of a pea (not in small fragments or in powder) and add to it half a part of oxygenated muriate of potash. Fill the vessel with water, and bring carefully into contact with the materials at the bottom of the fluid three or four parts of concentrated sulphuric acid. This may be most conveniently done, by letting the acid fall through a long-necked funnel, reaching to the bottom of the vessel, or by causing it to pass down the sides of it. As soon as the decomposition of the water and that of the oxygenated muriate takes place, flashes of fire dart from the surface of the fluid, and the phosphuret illuminates the bottom of the vessel with a beautiful green light.

EXPERIMENT V.

A riband or piece of silk, impregnated with a solution of muriate of gold, may be gilt by the action of phosphorated hydrogen gas,

Take a silk riband, wet it thoroughly with a solution of muriate of gold, and expose it over mercury to the action of phosphorated hydrogen gas for a few days; the riband in this situation will become covered with gold. The gilding is so permanent that it will bear washing.

RATIONALE...The hydrogen of the phosphorated hydrogen gas unites to part of the oxyd of gold dissolved in the acid, and forms water. The phosphorus thus separated unites to another part of the oxygen, and produces phosphoric acid. The gold therefore on losing its oxygen totally becomes reduced to the metallic state, and attaches itself by virtue of a strong molecular attraction to the riband.

REMARK.... One part of the crystallized muriate of gold dissolved in eighteen parts of distilled water, seems to answer this purpose extremely well.

If the gilding be repeated a second, or even a third time, its lustre becomes extremely beautiful.*

EXPERIMENT VI.

Phosphorated hydrogen gas and sulphureous acid gas decompose each other.

Let phosphorated hydrogen gas and sulphureous acid gas, both obtained over mercury, be mingled together, the two gases will lose their elasticity; plates of yellow matter are deposited on the sides of the vessel, which take fire on hot iron, first in the manner of phosphorus, and afterwards with the characters of sulphur.

RATIONALE....It follows from this experiment that the hydrogen is the only substance which combines with the oxygen in these circumstances, since the gases lose their fluidity and deposit respectively the sulphur and phosphorus contained in them.

* Mrs. Fulhame invented this experiment. T. C.

EXPERIMENT VII.

Phosphorated hydrogen gas is decomposed by vivid light

Though phosphorated hydrogen gas may be kept over mercury in the dark for any length of time unaltered, this is not the case if the gas be exposed to light. If a bottle filled with this gas be painted partly black, or surrounded with black paper, and then exposed to the light of the sun, the union of the phosphorus and hydrogen will be broken, and the phosphorus will be found crystallized at those parts through which the rays of light were suffered to pass, and the hydrogen gas will be left behind.

NITROUS GAS.

PART XXV.

SECT. I.

THE name of nitrous gas is given to an aeriform fluid, consisting of a certain quantity of nitrogen gas and oxygen: first described by Priestley, but in some measure known before to Hales.

PROPERTIES OF NITROUS GAS.

It

Nitrous gas is an elastic colourless fluid, having no sensible taste it is neither acid nor alkaline; it is exceedingly hurtful to animals, producing instant suffocation whenever they attempt to breathe it. The greater number of combustible bodies refuse to burn in it. is nevertheless capable of supporting the combustion of some of these bodies. Phosphorus burns in nitrous gas when introduced into it in a state of inflammation; pyrophorus takes fire in it spontaneously.

It is not decomposable by water; though 100 cubic inches of this fluid, when freed from air, absorb about 11.8 cubic inches of gas. This solution is void of taste; it does not redden blue vegetable colours; the gas is expelled again when the water is made to boil or suffered to freeze. It has no action on nitrogen gas even when assisted by heat. It is decomposed by several metals at high temperatures.