In taking cognizance of water in relation to blowpipe analysis, we regard it only as existing in minerals. The examination for water is generally performed thus: the substance may be placed in a dry tube, and then submitted to heat over a spirit-lamp. If the water exists in the mineral mechanically it will soon be driven off, but if it exists chemically combined, the heat will fail to drive it off, or if it does, it will only partially effect it. The water will condense upon the cool portions of the tube, where it can be readily discerned. If the water exists chemically combined, a much stronger heat must be applied in order to separate it. Many substances may be perhaps mistaken for water by the beginner, such as the volatile acids, etc. (2.) _Nitric Acid_ (NO^{5}).--Nitric acid occurs in nature in potash and soda saltpetre. These salts are generally impure, containing lime, as the sulphate, carbonate and nitrate, and also iron in small quantity. The soda saltpetre generally contains a quantity of the chloride of sodium. The salts containing nitric acid deflagrate when heated on charcoal. Substances containing nitric acid may be heated in a glass tube closed at one end, by which the characteristic red fumes of nitrous acid are eliminated. If the acid be in too minute a quantity to be thus distinguished, a portion of the substance may be intimately mixed with some bisulphate of potash, and treated as above. The sulphuric acid of the bisulphate combines with the base, and liberates the nitric acid, while the tube contains the nitrous acid gas. The nitrate of potassa, when heated in a glass tube, fuses to a clear glass, but gives off no water. When fused on platinum wire, it communicates to the external flame the characteristic violet color. When fused and ignited on charcoal, its surface becomes frothy, indicating the nitric acid. (3.) _Carbon_ (C).--Carbon is found in nature in the pure crystallized state as the diamond. It occurs likewise in several allotropic states as graphite, plumbago, charcoal, anthracite, etc. It exists in large quantities combined with oxygen as carbonic acid. The diamond, although combustible, requires too high a heat for its combustion to enable us to burn it with the blowpipe. When excluded from the air, it may be heated to whiteness without undergoing fusion, but with the free access of air it burns at a temperature of 703° C, and is converted into carbonic acid. If mixed with nitre, the potassa retains the carbonic acid, and the carbon may be thus easily estimated. If a mineral containing carbonic acid is heated, the gas escapes with effervescence, or a strong mineral acid as the hydrochloric will expel the acid with the characteristic effervescence.