115 On the H^iantity of Sutphut 



fonie importance. But whatever reafon there was to think, 

 by aiguing upon its chemical properties, that 1 had really 

 fuccccded in improving its medicinal viriues, it lliil re;-:iined 

 to be proved, by actual experiment, ihat the hoped-for luccefs 

 va-snot merery conjectural. To afcertain this, I gave fome 

 of inv powder to Dr. Crichton, Dr. Babinglon, and jSIr. 

 Aberi:et'iv; gentlemen whofe extenfive praAice and acknow- 

 ledged flc il futBciently enabled them to judge of its medical 

 properiies. They all concur in opinion, that, in its general 

 t'fleAs, it agrees with Dr. James's powder and the ptilvis an- 

 titnoniaUs') but that it is more mild, and confequently may 

 be given in larger quantities, feldom producing naufea or 

 vomiting in dofes of Icfs than eight or ten grains. 



XVfU. Obfcrvalhm and Experiments undertaken iv'itb a 

 View to determine the Quantity of Sulphur contained in 

 Sulphuric Acid; and of this latter contained in Sulphates 

 in general. Bj RlCHARD CHE^EVIX, E/q. F.R.S. 

 M^RJ-A."-' 



I 



N a paper which I had the honour to prefent to the Royal 

 Society of London, and the fubjeA of which was the analyfis 

 of fome arfcniates of copper and of iron, I had occafion, 

 in examining many pvritc^, matrices of thofe ores, to remark 

 the very great inequality which prevailed in the refults of re- 

 peated 'experiments, made with a view to determine the pro- 

 portion of fulphur. But I loon perceived that the inaccuracy 

 Was caufed by a partial combultion and acidification of the 

 ladical, through the means of the nitric acid employed to 

 dillolve the ore. 



Having therefore, in the ufual manner, afcertained what 

 ■quantity of that ingredient remained untouched, T was forced 

 to feek the reft of it in the liquor which had wafhed the va- 

 rious precipitates. To obtain it, I poured a folution of ni- 

 trate of barytcs into thofe wafliings when all the other fub- 

 ftances had been carefully feparatcd, and was thereby enabled 

 to precipitate, in a Itate of purity, the fulphate of barj-tes, 

 formed bv that earth, and by the portion of fulphur origi- 

 iially acidified in the firft treatment of the ore by nitric acid. 

 To come at the knowledge of the proportion of fulphur con- 

 tained in a given 'quantity of fulphate of barytes, I had re- 

 courfe, in the firft inftance, to the quantity of fulphur faid 

 by Lavoificr to be contained in fulphuric acidj and, in the 



♦ From die tianfuii'wr.s if tbc Rxal Injb Acadctnj, 



6 ' next, 



J 



