2 HISTORICAL INTRODUCTION. 



was than another. But to estimate the quantity 

 of real acid contained in each of those liquids, 

 another process was necessary. And he pro- 

 ceeded in this way : He took an ounce of salt of 

 tartar (carbonate of potash of the shops) and 

 saturated it wiih each of his acid liquids, deter- 

 mining the weights of each necessary to produce 

 the required effect. The liquid was then eva- 

 porated to dryness, and the dry salt left was 

 weighed. The augmentation of weight which 

 the ounce of salt of tartar had sustained, marked, 

 in his opinion, the weight of acid which had 

 combined with it. For example : 1 ounce of 

 salt of tartar when saturated with nitric acid 

 becomes 1'45 ounces. Hence he concluded that 

 saltpetre is a compound of 



Potash 100 * 



Nitric acid 45 



145 



In the same way he estimated the composition 

 of muriate of potash, sulphate of potash, acetate 

 of potash. It is unnecessary to give the results 

 which he obtained, because Homberg, not having 

 been aware that salt of tartar contained carbonic 

 acid, increased the amount of the potash, and di- 

 minished that of the nitric acid by the whole quan- 

 tity of carbonic acid previously united with the 



* Mem. Paris, 1699, p. 48. 

 3 



