METHODS OF OBTAINING OXIGEN GAS.

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The act of its combining with bodies is called oxidation, or ox-igenation ; and the bodies with which it is combined are calledoxids.

Oxigen gas is the chief basis of the pneumatic doctrine of che-mistry.

METHODS OF OBTAINING OXIGEN GAS

We are at present acquainted with a great number of bodiesfrom which we may, by art, produce oxigen gas. It is most am-ply obtained from the oxids of manganese, or mercury ; fromnitrate of potash ; from the green leaves of vegetables, and fromoxigenated muriate of potash, or soda. Besides these, there area great many other substances from which oxigen gas may beprocured.

1. In order to procure oxigen gas in a state of great purity,pure oxigenated muriate of potash or soda, must be made use of.With this view put some of the salt into a small earthen orglass retort, the neck of which is placed under the shelf of thepneumatic trough filled with water; and heat the retort by meansof a lamp. The salt will begin to melt, and oxigen gas will beobtained in abundance and of great purity, which mav be collectedand preserved over water.

Rationale. ..Oxigenated muriate of potash consists of oxige-nated muriatic acid and potash; at an elevated temperature adecomposition of the oxigenated muriatic acid takes place; itsoxigen unites to the caloric and forms oxigen gas. The oxigen-ated acid becomes therefore converted into simple muriatic acid,which remains in the retort united to the potash, in the formof muriate of potash.

2. Oxigen gas may likewise be obtained from the green leavesof vegetables.

For this purpose fill a bell-glass with water, introduce freshgathered green leaves under it, and place the bell or receiverinverted in a vessel containing the same fluid ; expose the