for

gen oxygen increased to a greater extent. A new attraction likewise takes place, namely, that of nitrous gas for nitric acid to form nitrous vapour,* and a new arrangement of principles is rapidly produced: the nitrogen of the ammonia having no affinity for any of the single principles at this temperature, enters into no binary compound; the oxygen of the nitric acid forms water with the hydrogen, and the nitrous gas combines with the nitric acid to form nitrous vapour.

All these substances most probably exist in combination at the temperature of their production; and at a lower temperature assume the form of nitrous acid, nitrous gas, nitrogen, and water; and hence we see the necessity of not heating the nitrate of ammonia above the beforestated temperature.

On account of the rapid absorption of gaseous oxyd of nitrogen by water, it is economical to preserve the fluid which has been used to confine this gas, and to make use of it for collecting other quantities of it. In order to hasten its production, the nitrate of ammonia may be previously freed from its water of crystallization by gently fusing it in a glass of Wedgwood's basin for a few minutes, and then keeping it for use in a well-stopped bottle.

2. Nitrous oxyd may likewise be obtained by exposing common nitrous gas to alkaline sulphites, particularly to sulphite of potash containing its full quantity of water of crystallization. The nitrous oxyd produced from nitrous gas by sulphite of potash, has all the properties of that generated from the decomposition of nitrate of ammonia.

RATIONALE....The conversion of nitrous gas into nitrous oxyd by these bodies, depends on the abstraction of a portion of its oxygen by the greater affinity of the sulphite presented to it. The nitrogen and remaining oxygen assume a more condensed state of existence, and constitute nitrous oxyd.

3. Nitrous oxyd may also be obtained by mingling together nitrous gas and sulphurated hydrogen gas. The volume of gases in this case is diminished, sulphur deposited, ammonia, water, and nitrous oxyd are formed.

RATIONALE....The change of principles which takes place in this experiment depends upon the combination of the hydrogen of the sulphurated hydrogen gas with dif

* Hence the reddish vapour in the retort, stated before, p. 324.

ferent portions of the oxygen and nitrogen of the nitrous gas, to form water and ammonia, and to deposit sulphur. The remaining oxygen and nitrogen being left in due proportion to constitute nitrous oxyd.

REMARK....This singular exertion of attractions by a simple body appears highly improbable, a priori; but the formation of ammonia, and the non-oxygenation of the sulphur, elucidate the fact. In performing this experiment, care should be taken that the gases should be rendered as dry as possible; for the presence of water considerably retards the decomposition.

4. Nitrous oxyd may also be produced by presenting alkaline sulphurets to nitrous gas. Davy observed that a solution of sulphuret of strontia or barytes answers this purpose best.

RATIONALE....This decomposition of nitrous gas is not solely produced by the abstraction of oxygen from the nitrous gas to form sulphuric acid. It depends equally on the decomposition of the sulphurated hydrogen dissolved in the solution or liberated from it. In this process sulphur is deposited, and sulphuric acid formed.

5. Nitrous oxyd is obtained in many circumstances similar to those in which nitrous gas is produced. Dr. Priestley found that nitrous oxyd was evolved, together with nitrous gas, during the solution of iron, tin, and zinc, in nitric acid.

RATIONALE....It is difficult to ascertain the exact rationale of these processes, for very complicated agencies. of affinities take place. Either the nascent hydrogen arising from the decomposition of the water by the metallic substance may combine with portions of the oxygen and nitrogen of the nitrous gas; and thus by forming water and ammonia, convert it into nitrous oxyd; or the metallic substance may attract at the same time oxygen from the water and nitrous gas, whilst the nascent hydrogen of the water seizes upon a portion of the nitrogen of the nitrous gas to form ammonia. The analogy between this process and the decomposition of nitrous gas by sulphurated hydrogen, renders the first opinion most probable.

Such are the principal methods of obtaining nitrous oxyd. There are no reasons, Davy thinks, for supposing that nitrous oxyd is formed in any of the processes of nature; and the nice equilibrium of affinity by which it is

constituted forbids us to hope for the power of composing it from its simple principles. We must be content to produce it artificially.

SECT. II.

EXPERIMENTAL PROOFS OF THE PROPERTIES OF GASEOUS OXYD OF NITROGEN.

EXPERIMENT I.

Gaseous oxyd of nitrogen is rapidly absorbed by water.

FILL a glass cylinder or graduated tube with water previously boiled, and invert it in a basin of the same fluid. Having done this, send up into it a quantity of nitrous oxyd, and mark the level of the water in the cylinder. Then agitate it for a few minutes in the water, and the bulk of the gas will be seen considerably diminishing. Water may thus be made to absorb about one half of its own bulk of gaseous oxyd of nitrogen.

On boiling the water, the gas which was absorbed will be liberated, possessing all its former properties.

If nitrous oxyd be repeatedly exposed to water, the residual gas will be the common air previously contained in the water, and from which it can in no case be perfectly freed by ebullition; this air becomes separated on account of the greater affinity of water for nitrous oxyd.

The quantity of common air thus produced generally amounts to about part of the volume of water.

The absorption of nitrous oxyd by the inflammable fluids enumerated before may be evinced in a similar manner. (See Appendix No. 27.)

EXPERIMENT II.

Combustible bodies do not burn in gaseous oxyd of nitrogen, except when in a state of actual inflammation.

Fill a jar over mercury with gaseous oxyd of nitrogen, and keep it over that fluid; introduce into it a small piece

of sulphur, camphor, or phosphorus, and touch these substances with a bent wire heated to a dull redness. The sulphur, camphor, or phosphorus, will melt, and continuingt he heat may even be made to sublime in the gas, but no accension will take place.

But that the gas is capable of maintaining the combustion of inflammable substances becomes evident from the following facts:

EXPERIMENT III.

Combustion of the taper in gaseous oxyd of nitrogen.

Immerse a lighted taper into a jar filled with nitrous oxyd. The flame of the taper will become instantly larger; it will first burn with a brilliant white flame, and sparkle as in oxygen gas. As the combustion goes on, the lustre of the flame diminishes; it gradually lengthens, and becomes surrounded with a pale blue cone of light, from the apex of which much unburnt charcoal is thrown off in the form of smoke. The flame continues double to the end of the process.

EXPERIMENT IV.

Combustion of phosphorus in gaseous oxyd of nitrogen.

Put a piece of phosphorus of the size of a pea into a copper ladle, set fire to the phosphorus with a match, and quickly introduce it into a jar filled with the gas. The phosphorus will continue to burn with a splendour nearly equal to that in oxygen gas.

The accension of phosphorus may likewise be evinced in the following manner.

EXPERIMENT V.

Fill a strong glass cylinder over mercury, one-eighth full of gaseous oxyd of nitrogen; send up into it a few

grains of phosphorus, heat a bent iron wire white-hot, and introduce it quickly through the mercury to touch the phosphorus, which thus will take fire instantly with a considerable detonation.

REMARK....This experiment requires caution: the cylinder in which the phosphorus is inflamed should be very strong. The gaseous oxyd employed should not exceed one-eighth of the capacity of the jar. The wire for the inflammation ought to be very well curved, so as to be expeditiously introduced into the jar, and capable of being quickly withdrawn. We have witnessed several accidents where the detonating jar burst during this experiment.

Another very successful method is as follows.

EXPERIMENT VI.

Let the jar containing the gaseous oxyd of nitrogen be placed over mercury; introduce the phosphorus in a small tube containing oxygen gas, so balanced as to swim on the surface of the mercury without communicating with the gaseous oxyd. The phosphorus is then fired in the oxygen gas with an ignited iron wire; by which, at the moment of combustion, the tube containing it must be raised into the gaseous oxyd, and thus the combustion continues.

EXPERIMENT VII.

Sulphur burning with a feeble blue flame becomes instantly extinguished in gaseous oxyd of nitrogen.

Put a piece of sulphur into a copper ladle, set fire to it by means of a candle, and when it begins to burn with a blue feeble flame, introduce it into a jar filled with gaseous oxyd of nitrogen. The sulphur will be extinguished the instant it is plunged into the gas.

But that sulphur may be made to burn in it becomes obvious from the following

EXPERIMENT VIII.

Sulphur, in a state of vivid inflammation, burns with a, rose-coloured flame in gazeous oxyd of nitrogen.

Dip a slip of copper into melted sulphur ; when cold set fire to it, and when in an actual state of combustion