124

COMPOSITION

MRS. B.

They are volatile oils, that have been acted on,and peculiarly modified, by oxygen.

CAROLINE.

They are, therefore, oxygenated volatile oils ?

MRS. b. ,

' Not exactly ; for the process does not appear toconsist so much in the oxygenation of the oil, as inthe combustion of a portion of its hydrogen, and asmall portion of its carbone. For when resins areartificially made by the combination of volatile oilswith oxygen, the vessel in which the process is per-formed is bedewed with water, and the air includedw ithin is loaded with carbonic acid.

EMILY.

This process must be, in some respects, similarto that for preparing drying oils ?

MRS. B.

Yes; and it is by this operation that both of themacquire a greater degree of consistence. Pitch, tar,and turpentine, are the most common resins; theyexude from the pine and fir trees. Copal , mastic,