1815.J On Todine. 198 
state of neutrality. It may even pass it, and assume the characters 
of acids, as happens to the peroxides of tin and antimony. 
In what I bave said I have supposed that oxygen communicates 
acidifying properties to other bodies; and I was the better entitled 
to make this supposition, because, though Sir H. Davy thinks that 
the chlorates and iodates contain no acid, and are triple compounds 
of the metals, oxygen and chlorine or iodine, | have demonstrated 
that they are true salts, analogous to the sulphates and nitrates, and 
that chloric and iodic acids may be obtained in a separate state. I 
do not refuse, however, to chlorine and iodine the acidifying pro- 
perty ; I go even further, and assign it to sulphur, which in my 
opinion possesses it in a high degree, to phosphorus, carbon, and 
several other bodies. I have long considered an acid, in its most 
general acceptation, as merely a body (whether it contains oxygen 
or no) which neutralizes alkalinity ; and an alkali is merely a body 
which neutralizes acidity. ‘Thus in the soaps the oil performs the 
function of acid, since it saturates alkalies; and in certain ethers 
the alcohol performs the function of an alkali, since it saturates 
acids. Knowing the elements of hydro-sulphuric acid and am- 
monia, and the observations of M. Berthollet on prussic acid, we 
cannot refuse to admit that a body may be acid or alkaline without 
containing oxygen, and consequently that acidity and alkalinity may 
be communicated by other bodies besides oxygen. ‘These observa- 
tions, by generalizing our notions of acids and alkalies, have ren- 
dered the definition of them very imperfect; because acidity and 
alkalinity are correlative terms, and one cannot be defined without 
recourse to the other. The difficulty of tracing a limit between the 
acids and alkalies is still increased when we find a body sometimes 
performing the functions of an acid, sometimes of an alkali. Nor 
can we diminish this difficulty by having recourse to the beautiful 
law discovered by Berzelius, that oxygen and acids go to the posi- 
tive pole; and hydrogen, alkalies, and inflammable bases, to the 
negative pole. We cannot, in fact, give the name of acid to all the 
bodies, which go to the first of these poles, and that of alkali to 
those that go to the second: and if we wished to define the acids 
by bringing into view the nature of their electric energy, it must be 
seen that it would be necessary to compare them with the electric 
energy which is opposite to them. Thus we are always reduced to 
define acidity by the property which it has of saturating alkalinity ; 
because acidity and alkalinity are two correlative and inseparable 
terms. 
Whatever definition of acid we prefer, we must divide the acids 
into different groups, because they do not all derive their acid cha- 
racter from the same body. We have, 
1. The acids properly so called, in which we may consider oxygen 
as the acidifying principle, and which contain only two elements. 
Such are chloric, iodic, sulphuric, sulphurous, nitric, nitrous, 
phosphoric, phosphorous, carbonic, arsenic, boracic, and probably 
Vor, VI, N? JIL, N 
