EXPERIMENTS ON SULPHURIC ACID. 131 



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

 contained 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 repeat my experiments. Nor mould 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 expect to fee the errors of our 

 predeceffors corrected by men, much inferior in abilities ; but 

 who, by pofTefling more certain means, fupply the want of 

 genius and invention. At the time in which the experi- Former experi- 

 ments were made, that determined the proportion of 33 per ^"J*^^^ 

 cent, of fulphuric acid in fulphate of barytes, it was not known becaufe barytes 



that we had never obtained any barytes pure ; and that a con- had not then 

 /•lit . /. /.« V , «• /• b^en obtained 



liderable portion of carbonic acid refitted the action ot every pure> 



degree of heat that had been applied to carbonate of barytes. 

 The fact 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 fyn- 

 thetic experiments, by combining, directly or indirectly, ful- 

 phuric 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 caufes may exift which are capable of accounting and becaufe La- 

 for any variation, whether in plus or in minus, that might have ^1 \"f P hu r \™~ 

 appeared in the experiments, by which Lavoifier determined oxigen, 

 the quantity of fulphuric acid, obtained by the combuftion of 

 fulphur in oxigen gas. 



lit. A part of the fulphur may be volatilized during com- might have vo- 

 buftion. lati2td fome > 



2d. All the fulphur may not be converted into fulphuric and " mperfedly 



•it. '. - . ,. r . . . . acidified fome, 



acid ; but part may remain in the ttate or tulphureous acid. 



3d. In rectifying, fome acid may come over along with the and been embar- 

 water; or, vice verfa, fome water remain with the acid. [* IC &\f ying." 

 Thefe confiderations will excufe me for having propofed a 

 doubt where the authority of fo great a man exifts againft the 

 experiments which I have related. 



K 2 The 



