ii6 On the Qua7Hilji of Sulphur 



excefs of acid j and the entire quantity of fulpliate of barytes 

 was dcpolitcd. Of the e.\ac\nefs of all thcfe methods, which 

 I uled as the inftruments by which I afccrtained thefe refults, 

 I convinced mvlelf by various preliminary experiments- 

 After the ufiial lillration, wa(hing and drying at the gentle 

 heat of a fand-bath, I obtained in one experiment 185, in 

 another 183, and, laftly, in another 180. This difference 

 docs not exceed the limits of what all perfons converfant in 

 analytic chemillry will allow to experiments of this nature. 

 We may therefore take 183 as the mean proportion; confe- 

 quently we fliall fay, that 183 of fulphate of barytes contain the 

 fame quantity of fulphuric acid as ico of fulphate of lime; and 

 183 : 43 : : 100 : 23.5. 'rherctore 23.5 is the proportion of 

 acid in 100 of fulphate of barytes. But we have before feen 

 that 14.5 of fulphur, acidilied bv nitric acid, form that por- 

 tion of fulphuric acid contained in 100 of fulphate of barytes, 

 viz. 23.5. \A'c mult now fav, that 23.5 : 14.5 : : 100 : 61.5, 

 and tlio fourth term will be the proportion of lulphur = 61 .5, 

 which combined with 38. 5 of oxygen will form 100 of real 

 fulphuric acid. 



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

 contained in the fait, or of the combudible bails contained 

 in the acid, do I agree with the two chemills whom I have 

 quoicd. Ibis jultly excited fome doubts in my mind, and led 

 me to repent my experiments. Nor Ojould I yet be tho- 

 roughly faiisiicd, if 1 could not, upon other grounds than 

 bv fuppoling inaccuracy in them, account for the apparent 

 ditierences. We nuiit ever expeft to fee the errors of our 

 predecellbrs corre6~ted by men much inferior in abilities, but 

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

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

 ments 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 anv barytes pure; and that a 

 conPderable portion of carbonic acid refifted the action of 

 every degree of heat that had been applied to carbonate of 

 barvtes. The f;icl; was, I believe, firfi. obferved by i'clletier, 

 but tlic nictliod of avoiding the inconvenience was pointed 

 out by Vauquelin. He dccompofes nitrate of barvtcs by fire, 

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

 and the water. The chemills I have mentioned performed 

 fynthetic experiments by combining, directly or indiredtlv, 

 fidphurlc acid, and fueh barytes as they imagined to be pure. 

 The conllant fnnilarity of their refults is fufficient to prove 

 the accuracy of their operations; but, working upon an im- 

 pure fubltance, they muif have been contented with a fimi- 

 l^iity of errt)r. 



Three 



