NITROGEN. Azote, so called from its fatal effects on life when breathed, in an uncombined state. Hydrogen forms about seventy-nine parts in the one hundred parts of air. In combination with oxygen, it forms nitric acid. Combinei with hydrogen it forms ammonia. In combina tion with oxygen it is the source of nitrogenous compounds in animals and plants ; pure nitrogen is a colorless gas devoid of taste and smell. Thus we see that the air is the source of this necessary ingredient in plants and yet it is locked up, so far as the artificial elimination of it is concerned, at least from an economical point of view. Iu the state in which nitrogen exists in the air, it can not he assimilated by plants except through its foliage. Its only source to plants being through the roots either from geine, from ammonia, or from the nitrates, through decom position by the action of the growing plant. It has indeed been held that plants take up nitro gen, from the air by their leaves. There is however, no real proof that such is actually the fact. Nitre consists of an alkali united to an acid composed of one part of nitrogen to five of oxy _gen is in fact nitrate of potash. The nitrates of potash, soda, magnesia and lime are natural pro -ducts. The nitrates of oxides, and of metals are artificial products. The nitrates undergo decom position at a high heat, thus they are converted into free nitric acid and the oxidized base, or into oxygen which escapes, and into nitrous acid, which remains in combination with the base forming a nitrite. In the laboratory it is easy to produce nitrogen The air is simply to be deprived of its -oxygen. It may be done in various ways, either by leaving a piece of phosphoruS several days in a bell glass over water, or hy burning phosphorus in the glass standing over water, or by pass ing air through a tube partly filled with copper shavings, heated to a red heat. Nitric acid is
the most important product of nitrogen, and the agent from which the other compounds are pro -duced. Nitric acid when pure, occurs in bril liant transparent crystals, its composition in 100 parts being nitrogen twenty-six, and oxygen seventy-four parts. In commerce it is only found mixed with water, its most concentrated form, that of fuming acid being 85.72 parts of anhydrous acid 13.28 of water. Its most usual form in commerce is sixty per cent. of pure acid and forty per cent. of water. It is, however, of -various degrees of strength, often containing two-thirds of water. Nitrous acid is an unstable compound giving off deep red fumes. It is gen erated by the action of dilute nitric acid upon .copper shavings, deutoxide or nitric oxide being first formed which, exposed to the air, absorbs more oxygen. The lowest oxide of nitrogen is the protoxide or nitrous oxide. It has a sweet taste but no odor or color. Ammonia, one of the more important compounds of nitrogen is an infLammable gas, very pungent to the smell and acrid to the taste. It is readily and abundantly formed by decaying organic bodies, containing nitrogen, for, in the process of decay, the elements of organic matters form new groupings generally simpler than the original substances. Thus a portion of nitrogen associates with a portion of hydrogen, and ammonia is formed. In the case of heating manure, it is the pungent gas. In the decay and decomposition of human urine, car bonate of ammonia is formed. So the carbonate of ammonia is formed in the manufacture of bone black. Commercial ammonia is mostly formed by the distillation of bituminous coal, and is a bye product in making illuminating gas.