AND ON SOME SUBJECTS OF CHEMICAL THEORY. $13 
mon characteristic properties, and when these compounds all 
contain a common element, we conclude with justice, that 
these properties: are derived more peculiarly from the action of 
this element. On this ground Lavorsrer inferred, by an ample 
induction, that oxygen is a principle of acidity. Berrnotuer 
brought into view the conclusion, that it is not exclusively so, 
from the examples of prussic acid and sulphuretted hydrogen. 
In the latter, acidity appeared to be produced by the action of 
hydrogen. The discovery by Gay Lussac, of the compound 
radical cyanogen, and its.conversion into prussic acid by the addi- 
tion of hydrogen, confirmed this conclusion ; and the discovery 
of the relations of iodine still farther established it. And now, 
if the preceding views are just, the system must be still farther 
modified.. While each of these conclusions is just to a certain 
extent, each of them requires to be limited in some of the 
eases to which they are applied; and. while acidity is. some- 
times exclusively connected with oxygen, sometimes with hy- 
drogen,, the principle must also be admitted, that it is more 
frequently the result of their combined operation.. 
There appears even: sufficient reason to infer, that from the 
united action of these elements, a higher degree of acidity is. 
acquired than from the action of either alone. Sulphur affords. 
a striking example: of this.. With hydrogen it forms a weak: 
acid. With oxygen it also forms an acid, which, though of su- 
_ perior energy, still does not display much power. With hy- 
drogen and oxygen it seems to receive the acidifying influence: 
of both, and its acidity is proportionally exalted. 
Nitrogen with hydrogen forms a compound altogether desti- 
tute of acidity, and possessed even of qualities’ the reverse. 
With oxygen in two definite proportions, it forms oxides; 
and it is doubtful, if in any proportion, it can establish with 
oxygen an insulated acid.. But with oxygen and hydrogen in 
Vou. VIII. P: IL Rr ~~ union 
