ORGANIC SUBSTANCES. 675 
nexion exists between a compound radical and its conjunct, we 
can easily conceive how impossible it is to ascertain the relation- 
ship. 
The grand difficulty in the application of the idea of compound 
radicals to the critical examination of the rational composition 
of organic compounds, consists in ascertaining whether the sub- 
stance under examination is a single organic oxide or a conju- 
gate compound. In the first case it is easy to obtain a notion 
of the radical, in the last it is impossible, for the active oxide 
has its radical, as has also the conjunct; and when the conjunct 
is a compound of two substances, each of these has likewise its 
radical. It is thus evident that the idea of compound radicals 
may be quite correct and yet not applicable under such circum- 
stances, until we have obtained some knowledge of the compo- 
sition both of the active oxide and of the conjunct. When this 
knowledge is unattainable, which it is in most cases, we must, 
as I have already noticed, consider the organic substance em- 
pirically as a single whole. 
The number of compound radicals may perhaps not be very 
great; for it is possible that the endless multiplicity is produced 
by changes in the conjugate compounds. We have nearly 100 
different acids into the composition of which sulphuric acid 
enters, only varying according to the different conjuncts which 
they contain. 
I have already mentioned, that when the number of oxygen 
atoms in an organic atom exceeds seven, we have reason to pre- 
sume that the compound belongs to the conjugate class of com- 
binations, in which the conjoined amount of oxygen in the con- 
joined oxides together, may sometimes increase the atomic pro- 
portion of that element considerably. It occasionally happens 
that the amount of oxygen in these compounds may be lessened 
or increased. When this, however, only takes place with one 
of the combined oxides, the change never amounts to more than 
a small fraction of the whole quantity of oxygen contained in 
the combined oxides, and does not correspond with the multiple 
proportions which we are in the habit of meeting with in inor- 
ganic chemistry; but it is evident that it would correspond to 
these if we could calculate it for the oxide to which it appertains. 
Thus, for instance, proteine contains 10 atoms of oxygen, but 
the amount of oxygen can be raised by 2 or 3 atoms, to bin- and 
tritoxide of proteine with 12 and 13 atoms of oxygen. This un- 
VOL. IV. PART XVI. 3B 
