COMPOSITION OF PLANTS. 



356. 



Mild oil passes into a kind of wax, when it is slightly oxi- 

 dated, and attains, by that means, a certain degree of firmness ; 

 for art can produce wax from oil by nitric acid, and can change 

 it into oil again, by taking away the acid. Wax is produced 

 by Nature herself, in the fruit of the Stillingia sebiferay 

 Rhus succedanea, Myrica cerifera^ and in the bark of the 

 Wax-palm {Ceroxykm Andicola). 



357. 



Volatile oils, which are commonly united with extractive 

 matters, are distinguished from mild oils, by containing a 

 greater proportion of hydrogen than of carbon. Of the for- 

 mer substance, they seem to contain, in many cases, two- 

 thirds, or even three-fourth parts. It is remarkable that 

 they are chiefly found in the covers of seed 3, and, in the case 

 of the Scitamineae, in the vitellus even, but almost never in 

 the albuminous bodies, and in the cotyledons of the embryons. 

 When volatile oils are oxydated, they run into a hard sub- 

 stance, which is called Camphor, and in which it has been 

 supposed that a peculiar acid resides, although good chemists 

 consider it as the sarne with the benzoic acid. This last sub- 

 stance is found in most of the balsams, or in those bodies 

 which, beside volatile oil, contain also resinous extract. The 

 strong smell of this acid, and its inflammability, as well as its 

 weak affinity to the alkaline base, point it out as rich in hy- 

 drogen. 



The volatile oils pass through the balsams into resin ; be- 

 cause, by evaporation and the application of acids, we can 

 procure these oils from resinous substances. 



358. 



We must now consider those bases in plants which can be 

 united with acids, — the origin of which is involved in much 

 obscurity. 



With respect to the alkalies, it is certain that potassa 

 is one of the most common substances to which the vege- 

 table acids are united ; but it is undoubtedly not drawn 



