AND ON SOME SUBJECTS OF CHEMICAL THEORY. 813 



mon characteristic properties, and when these compounds all 

 contain a common element, we conclude w T ith justice, that 

 these properties are derived more peculiarly from the action of 

 this element. On this ground Lavoisier inferred, by an ample 

 induction, that oxygen is a principle of acidity. Berthollet 

 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 

 cases 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 

 Vol. VIII. P. II. R-r union 



