1822.] Sixth Edition of his System of Chemist r;^, 251 



labours of their predecessor will almost always enable them to 

 approach somewhat nearer the truth than he did. To the 

 labours of Berzehus I have always acknowledged myself greatly- 

 indebted. They are (all things considered) surprisingly accu- 

 rate ; nor should I have been able in many cases to have obtained 

 good results without their assistance. If I have come nearer the 

 truth than he has done, it w as only because I was enabled to 

 profit by his experiments. 



As for Dr. Wollaston, the introduction of his name is most 

 uncandid. His scale of chemical equivalents v/as constructed 

 not from his own experiments, but from those of others. He 

 examined them with his usual sagacity, and the numbers which 

 he pitched upon approach in general very near the truth. Hia 

 paper contains only a single experimental result of his own; 

 namely, the composition of saltpetre; by which he determined 

 the equivalent for 7iitric acid and azote. Now the fact is, that 

 I have adopted almost the very atomic weights of these bodies 

 which he had previously given. My obligation to him for these 

 numbers had been distinctly stated in my former papers ; conse- 

 quently I had no occasion to allude to the subject again. 

 Besides, in my paper on the specific gravity of the gases, I 

 deduced the atomic weights of azote and its compounds in a 

 different way ; but in a way which I consider as very satis- 

 factory. 



As a specimen of the uncandid way in which my observations 

 have been represented by the Reviewer, I may notice the ridi- 

 cule which he throws on my statement, that acids are compounds 

 of a supporter and combustible or incombustible. Now 1 ask, 

 is not this observation true with a very few exceptions ? We are 

 at present acquainted with 50 acids to which it apphes correctly. 

 There are two acids, the chloric and iodic, which are composed 

 each of two supporters of combustion. In these two acids, I 

 consider the chlorine and iodine to act precisely the part which, 

 azote does in nitric acid. This is the view which the French 

 chemists have taken, and it has induced them to place both 

 chlorine and iodine among the combustibles. I have given my 

 reasons for preferring my own arrangement ; but I admit that ia 

 these acids the chlorine and iodine act the part of simple incom- 

 bustibles. I do not, therefore, regard their existence as aa 

 exception to the general law, but as proving that chlorine and 

 iodine may be considered under two points of view, either as 

 supporters of combustion, or incombustibles. It is this double 

 capacity of these bodies that constitutes the great distinction 

 between them and oxygen. 



There is another set of gaseous bodies capable of uniting with 

 bases, and often on that account considered as acids. These 

 are the compounds of hydrogen with sulphur, selenium, and 

 tellurium. Now these bodies 1 have expressly separated in my 

 System. Whether my reasons for this separation be conclusive^ 



