13 



between monobasic andbibasic acids, &c. admits of a simple and easy 

 explanation by it. The leading propositions in those papers have been 

 adopted by several eminent chemists in this country and in France ; 

 and M. Gerhardt speedily enriched science with a series of brilliant 

 and striking illustrations of their truth. As regards the constitution 

 of bibasic acids, M. Gerhardt's results were, however, at variance 

 with that theory ; and he was led to represent them by formulae 

 equally inconsistent with his own previous views on the subject. I 

 believe that this discrepancy is satisfactorily removed by the facts I 

 have the honour of submitting to the consideration of the Society. 

 An atom of nitric acid, being eminently monobasic, is, as we have 



JT 



already shown, represented in the monobasic type ^,0 by the 

 formula ^ |rO, in which peroxide of nitrogen (NOJ replaces one 



.TT , 



atom of hydrogen. In like manner, hydrate of potash ( K O) is ob- 

 tained by replacing one atom of hydrogen in the type by its equiva- 

 lent of potassium ; and nitrate of potash ( vJ by a simultane- 



ous substitution of one atom of hydrogen by peroxide of nitrogen, 

 the other by potassium. Sulphuric acid is formed from two atoms of 



H 



water ^ ; one of hydrogen from each is removed, and the two 



H 



replaced by the indivisible radical SO 2 . The series 



Sulphuric acid. Acid sulphate of potash. Neutral sulphate of potash. 



H H K 



SO, . SO B0 



H K K 



explains itself. 



Chemists have long known how to remove the basylous consti- 

 tuents H, K, &c. of these salts, and to replace them by others. But 

 it is only recently that they have learnt to remove the chlorous 

 radicals SO 2 , NO 2 , &c. in a similar manner. To obtain the chloride 

 of potassium from its sulphate, it is sufficient to bring the latter into 

 liquid contact with chloride of barium ; but the same reagent would 

 be powerless for the preparation of the chlorides of the radicals SO 2 

 or NO 2 . 



