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METHODS 01 ' OBTAINING NITRIC ACID.

The following method of obtaining nitric acid is made use ofby chemists.

Take two parts of d-y nitrate of potash in coarse powder, putit into a tubulated glass retort, of which it occupies no morethan one-third, or one-fourth, and to which a large receiver hasbeen luted containing a little water; then pour on it, in smallquantities, at a time, one part of concentrated sulphuric acid.As soon as the last quantity of the acid is introduced into theretort apply a very gentle heat, and distil slowly till no moredrops issue from the neck of the retort. The acid collected inthe receiver is fuming and of a reddish or yellow colour: onbeing brought into contact with atmospheric air, it sends forthreddish-yellow fumes, which likewise always fill the empty spaceof the receiver or bottle. In order to deprive it of these fumes,the acid must be re-distilled, or at least heated for some time ina glass retort, with a very gentle heat; the fuming part will risefirst, and the remainder will be deprived of all its colour andfuming property.

Remark. ..The property of emitting reddish-yellow fumes*doesnot belong to the pure nitric acid, for this is one of the charac-teristics of another kind - of acid, called nitrous acid, which weshall presently consider. The fumes which are evolved are ni-trous gas, originating from a partial decomposition of a certainpart of the acid during its disengagement from the nitrate of pot-ash; hence it is soiled with nitrous gas. On exposing the acidto heat, or re-distilling it, this nitrous gas becomes disengaged,and pale nitric acid is obtained.

The combinations of nitric acid with different bases, are called

NITRATES,

PROPERTIES OF NITRATES.

These salts detonate with, or inflame charcoal, and other easilyinflammable bodies, at a red heat. They afford oxigen and