CHEMISTRY. 63 



obtained by distillation. Most of them are lighter than water, 

 highly combustible, and dissolve in alcohol to form essences: 

 when pure, they are colorless, and evaporate from paper 

 without leaving a greasy stain, as fixed oils do: they do not 

 form soap with alkalies, 



VEGETABLE ACIDS. 



Acids are numerous in the vegetable kingdom, and possess 

 much interest and importance ; but the limits of this book will 

 not admit of a detailed account of them : they constitute but a 

 small part of the plants from which they are derived. The 

 most important are the acetic, oxalic, tartaric, citric and malic 

 acids. The general properties of acids have already been 

 described. 



VEGETABLE ALKALIES. 



Alkalies exist in all plants, and always in the form of salts, 

 or in combination with an acid. Potash, lime and soda, 

 although found in plants in greater abundance than the 

 others, are not vegetable alkalies : the true vegetable alkalies 

 are, morphia, quinia, strychnia, <fec. 



METALLIC OXIDES AND EARTHS found in plants have already 

 been named, and their properties will be described in another 

 chapter. The few organic proximate elements of plants which 

 have been briefly described, are but a comparatively small 

 part of the whole number: only such as possess most interest, 

 and are most common and necessary to be understood, have 

 been selected. 



DIASTASE. 



Diastase is a white, tasteless powder, formed during the 

 process of malting barley, and also during the germination of 

 plants. The properties of diastase are not well understood, 

 it is supposed to be the first product of the putrefactive fer- 

 mentation of vegetable gluten and albumen. 



