[ 241 I 



In neither of the proportions, whether it be of the acid con- 

 tained in the fait, or of the combuftible bafis contained in the 

 acid, do I agree with the two chymifts whom I have quoted. 

 This juftly excited fome doubts in my mind, and led me to re- 

 peat my experiments. Nor fhould I yet be thoroughly fatisfied, 

 if I could not, upon other grounds, than by fuppofing inaccuracy 

 in them, account for the apparent differences. We muft ever 

 expecSl to fee the errors of our predeceflbrs correded by men, 

 much inferior in abilities; but who, by poffeffing more certain 

 means, fupply the want of genius and invention. At the time 

 in which the experiments were made, that determined the pro- 

 portion of 33 per cent, of fulphuric acid in fulphate of Barytes, 

 it was not known that we had never obtained any Barytes pure } 

 and that a confiderable portion of carbonic acid refifted the a<3ion 

 of every degree of heat that had been applied to carbonate of 

 Barytes. The fad was, I believe, firft obferved by Pelletier; but 

 the method of avoiding the inconvenience was pointed out by 

 Vauquelin. He decompofes nitrate of Barytes by lime, and a 

 moderate degree of heat is fufficient to expel all the acid and 

 the water. The chymifts, I have mentioned, performed fynthetic 

 experiments, by combining, diredly or indiredly, fulphuric acid, 

 and fuch Barytes as they imagined to be pure. The conftant 

 fimilarity of their refults is fufficient to prove the accuracy of 

 their operations ; but working upon an impure fubftance, they 

 muft have been contented with a fimilarity of error. 



Three 



