contained in Sulphuric Jlcid. 1 1 7 



Three caufi-s mav exift which are capable of accounting 

 For any variation, whether in plus or in minus, that might 

 have appeared in the experiments, bv which Lavoifier de'er- 

 mined the quantity of fuliihuric acid obtained by the eom- 

 buliion of fulphur in oxygen gas. 



id, A part of the fulphur may be volatilized during com- 

 biilHon. 



-d, All the fuljihur may not be converted into fulphuric 

 acid, but part may remain in the ftate of fulphureous acid. 



3d, In reAitying, fome acid may come over along with 

 the water; or, vice verjuy fome water remain with the acid. 

 1 hefe confiderations will cxcufc me for having propofed a 

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

 the experiments which I have related. 



The method which I had ufed to afcertain the quantity 

 of fulphur in an ore had been practil'ed by Taifaert [Aunales 

 lie Cbimie, No. 83: Analyfis of Cobalt from Tunabcrg); but 

 he calculated according to the proportions o*f Lavoilicr'and of 

 Foureroy. In another paper by Thenard, {Annalesde Cbi- 

 mie, No. 96,) he fiates the proportions of fuljjhuric acid, ob- 

 tained by treating fulphur with nitric acid, to be 

 Sulphur - - 55.56 



Oxygen - - 44.44 



loo.oa 

 but in the extract given by Guyton in that number of the 

 Annalcs dc Cbnint, the mode of operation is not dclcribed. 

 Calcined fulphatc of baryles is elUmateJ in the lame paper 

 to contain 



Earytes - - 74-8 z 



Sulphuric acid - 25. iS 



100.00 

 which proportion!? are as near to what I had found as can be 

 expeded ; for fidphatc, of baryles does not contain more than 

 3 per cent, of water of crydallizalion, and they mui'l be de- 

 ducted from the quintal. 



Having determined with accuracy the proportion of acid 

 in any infoluble fulpluite, it is eafy to proceed to the dflcr- 

 niination of that contained in any other fuiphate. 'I'hc do- 

 clmallic art, or analytic chemirtry, in general, cannot how- 

 ever expe6l to derive liieh advantages from the knowledge of 

 foluble faUs, as of thole which, from their infolubihtv, 

 may be ufed with accuraiy, in dcheate experiments, to de-- 

 lermine the proportions of the con diluent parts of bodies. 



