Book II. 
Dieovery. 
PRIMARY COMPOUNDS. 
phosphorous and phosphoric acids. In these cases one 
of the acids contains a greater proportion of oxygen 
than the other. The acid which contains least oxygen 
is distinguished by the termination ous, that which con 
tains most by the termination ic. Thus sulphurous 
acid contains a less proportion of acid than sulphuric 
acid. 
All the acids belonging to the second class are ob 
tained from the vegetable and animal kingdoms. The 
first twelve (omitting lactic acid) have been denomina 
ted vegetable acids, because they all either exist ready 
formed in vegetables, or at least may be obtained from 
vegetable bodies. They are all composed of different 
proportions of carbon, hydrogen, and oxygen. In them 
the termination is arbitrary, and has no reference to the 
proportion of their oxygen. The three last have been 
called animal acids, because they can only be obtained 
from the animal kingdom. They possess the least of 
the acid character. 
An account of these different acids shall form the 
subject of the following Sections. 
SECT.I. 
OF SULPHURIC ACID. 
THE ancients were acquainted with some of the com 
pounds into which sulphuric acid enters ; alum, for in 
stance, and green vitriol: but they appear to have been 
ignorant of the acid itself. It is first mentioned in the