SECTION OF PNEUMATIC TROUGH.
The next compound of nitrogen with oxygen, when one proportion of nitrogen unites with two of oxygen, is termed nitric oxide gas. It may be easily procured by heating in a retort some copper turnings in dilute nitric acid. It is colourless and transparent, and has the property of combining with oxygen to form other compounds.
EXPERIMENT.
Into a jar of this gas standing over water pass some oxygen gas. The jar will be filled with red fumes, which will be rapidly absorbed by the water. If atmospheric air be used instead of oxygen, there will remain in the jar the nitrogen of the air, amounting to four-fifths of the air employed.
This gas is destructive to animal life, in consequence of its property of uniting with the oxygen in the lungs, and producing the highly corrosive nitrous acid gas. It will, however, support the combustion of a few substances, phosphorus for instance, provided it is sufficiently heated before being plunged into the gas.
We pass over the third and fourth compounds of nitrogen with oxygen, as they are not calculated for amusing experiments. Nitric acid is easily prepared on the small scale, by gradually heating equal parts by weight of nitric and sulphuric acid in a retort to which a receiver has been adapted. The receiver, which may be a clean oil flask, should be kept cool with wetted blotting paper.
Nitrogen combines with chlorine and iodine, forming detonating compounds, the former being so extremely dangerous that it will be better to pass it by.
The compound with iodine, called iodide of nitrogen, may very easily be made by pouring strong solution of ammonia (a compound of nitrogen and hydrogen) upon some iodine in a phial, shaking them well together, and after letting them stand for a few hours, pouring off the fluid; the black powder remaining in the phial is the explosive compound, the iodide of nitrogen. When dry, it is very apt to detonate spontaneously; it should therefore be shaken out of the phial while wet, and spread in very small quantities on separate pieces of blotting paper, which should be kept apart from each other. When thoroughly dry, the slightest touch with the point of a feather, shaking the paper on which it rests, or even opening too rapidly the door of a closet where it has been put to dry, will cause it to explode, producing a quantity of violet-coloured fumes. The explosion is somewhat violent, producing a sharp cracking noise; and the greatest care should be taken in experimenting with it.