190 On Sulphuric Acid and Naphthaline. [1826. 



were those of ammoniacal salts. When its solutions, though 

 previously rendered alkaline, were evaporated to dryness at 

 common temperatures, and exposed to air, the salt hecame 

 strongly acid to litmus paper. This however is a property 

 common to all soluble ammoniacal salts, I believe, without 

 exception. 



Baryta. It is easy by rubbing carbonate of baryta with 

 solution of the impure acid, to obtain a perfectly neutral solu- 

 tion, in which the salt of baryta, containing the acid already 

 described, is very nearly pure. There is in all cases an undis- 

 solved portion, which being washed repeatedly in small quan- 

 tities of hot water, yields to the first portions a salt, the same 

 as that in the solution. As the washings proceed, it is found 

 that the salt obtained does not burn with so much flame on 

 platina foil, as that at first separated ; and the fifth or sixth 

 washing will perhaps separate only a little of a salt, which, when 

 heated in the air in small quantities, burns without flame in 

 the manner of tinder. Hence it is evident that there are two 

 compounds of baryta, which as they are both soluble in water, 

 both neutral, and both combustible, leaving sulphate of baryta, 

 differ probably only in the quantity of combustible matter pre- 

 sent, or its mode of combination in the acid. 



It is this circumstance, of the formation of a second salt in 

 small but variable quantities with the first, which must be 

 guarded against, as before mentioned, in the preparation of 

 salts from the impure acid. It varies in quantity according to 

 the proportions of materials, and the heat employed ; and I 

 have thought that when the naphthaline has been in large 

 quantity, and the temperature low, the smallest quantity is 

 produced. When the impure acid is used for the preparation 

 of the salts now under description, a small portion of it should 

 be examined by carbonate of baryta as above, and rejected if 

 it furnish an important quantity of the flameless salt. 



These bodies may be distinguished from each other provi- 

 sionally, as the flaming and the glowing salts of baryta, from 

 their appearances when heated in the air. The latter is more 

 distinctly crystalline than the former, and much less soluble, 

 which enabled me by careful and repeated crystallizations to 

 obtain both in their pure states. 



The flaming salt (that corresponding to the acid now under 



