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Three caufes may exift which are capable of accounting 

 for any variation, whether in plus or in m'lnus^ that might have 

 appeared in the experiments, by which Lavojfier determined 

 the quantity of fulphuric acid, obtained ^by the combuftion of 

 fulphur in oxygen gas. 



ift. A part of the fulphur may be volatilized during com^ 

 buftion, 



2d. All the Sulphur may not be converted into fulphuric 

 acid 5 but part may remain in the flate of fulphureous acid. 



3d. In re£tifying, fome acid may come over along with the' 

 water ; or, vice ver/i, fome water remain with the acid. Thefe 

 Gonfiderations will excufe me for having propofed a doubt, 

 where the authority of fo great a man exifts againft the ex- 

 periments which I. have related. 



The method which I had ufed to afcertain the quantity of 

 fulphur in an ore, had been pradifed by Taffaert, (Annales de 

 Ghimie,. No. 82: Analyfis of Cobelt from Tunaberg) but he 

 calculated according to the proportions of Lavoifier and of 

 Fourcroy. In another paper by Thenard, (Annales de Chimie, 



No.. 



