1^3$ X}tt j/ji^flni'tiy pf Sulphur In Sulphuric Jcld. 



than by fuppofjng iaaccuracy in thpro, account for the apparent .differences. We muft 

 ever expert to fee the errors of our predecefFors corrected by men, much inferior in abi- 

 lities ; but who, by pofleffing more certain means, fupply the want of genius and invention. 

 At the time in which the experimcjits were made, that determined the proportion 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 

 5ifl:ion of every degree of heat tliat had been applied to carbonate of barytes. The fad!t 

 V»s, I ^lieye, ,fu:ft obferved by Pelletier; but the method of avoiding the. inconvenience 

 was pointed outhy Vauquelin. He decompofes nitrj^te of barytes by fire, and a moderate 

 degree gf Iveot ^s fuilicient-to expel all the acid and ithe water. The chymifts I have men- 

 tioned, perf9^n\^f\ fynthetlp experiments, by combining, dire£t]y or indireftly, fulphuric 

 ji^jd, ,3«<J fwc.h h?>rytes as they imagined to bp pure. The cpnftaoi fimilarity of their refults 

 is fufficient tp prove the accuracy of their operations ; but working f^pon sm impure fub- 

 ftance, they muft have been contented with a fimilarity of error. 



Tliree caufes may exift which are capable of accounting for any variation, whether in 

 plus or in m»MJi, <hat; might have apppared in the -experiments, by.which Lavoifier deter- 

 mined the qqai^tity of fulphuric acid^ obtwaed._l|y the combuftion of fulphur in oxigen 



gas. . . • . ;,. 



tft, A part of the fulphur may be volatilized during combuftion. 



3d. All the fulphur may not be converted into fulphuric acid } but part may remain in 

 the ftate of fulphureous acid. . -_-i!.. 



3d. In reftifying, fome acid may come over along with th^ watery or, vkever/d, fomc 

 water remain with the acid. Thefe confideratlons will excufe mc for having propofed a 

 doubt, where the authority of fo great a man exifts. againfl: the experiments whidi I have 

 related. 



The method which I had ufed to afcertain the quantity of fulphur In an ore, had been 

 yvad^ifed by Taflaert, {Jnnalet de Chimie, No. 82 : Analyfis of Cobalt from Tunaberg) but 

 i^ calculated according to the proportions of Lavoifier and of Fourcroy. In another paper 

 by Thenard, {Jmmhs de Chimie, No. 96.) he dates the proportions of fulphuric acid, ob- 

 tained by treating fulphur with nitric acid, to be 



Sulphur - - - - 55'5<5 



Qyigen - - ^ - - 44.44 



too .00 

 tut in tlie extra(f^ given by Guyton in that No. of the Annalcs dc Chimk, the mode of ope- 

 ration is not defcribed. Cakined fulphate of barytes is eftlmated in the fame paper t* 

 contain 



Barytes . - • - * 74- 8a 



Sulphuric acad » - •• - 25.18 



100.00 



which 



