54^ On 'the ^lanttty if Sulphur in Sulphuric Acid, 



of error, therefore, remained open in this branch of the calculation; v.'hicli gave the pro- 

 portion of 23.43 of fulphur, as that contained in 100 parts of fulphate pf baryte?. ; . ; m 



However, before I would allawmyfelf to call in queftion fuch authorities as thofe I have 

 quoted, I inftituted the following experiments: in a tubulated glafs retort, I put 100 parts 

 of purified fulphur, and poured upon them ftrong nitric acid. A quilled receiver, plung- 

 ing into a Woulfe's apparatus, was adapted to the retort ; and, all being well luted, I pro- 

 ceeded to diftil. ; The liquor, which came over, was poured back feveral times upon the 

 fulphur, until the whole was diflblved. The water, which had come over, and that, 

 through which -the nitrous gas, produced during the operation, had pafled, were eflaycd 

 for Sulphureous acid, and no traces. of it could be found. No fulphur had been volatilized ; 

 therefore no fufpicion could remain, that all was not converted, into fulphuric acid. The 

 liquors, which were in the various parts of the apparatus, were united ; and to them was 

 added a fufficient quantity of nitrate of barytes. The whole was evaporated gently; be- 

 ca»fe, though I am well acquainted with the very little folubility of fulphate of barytes, I 

 well know that nitric acid will retain a fmall portion of it, particularly when formed in a 

 liquor where that acid abounds. In a firft experiment, I obtained 694 from 100 of fulphur ; 

 in a fecond, 348 from 5c; and in a third, 347 from the fame quantity. But the fimple 

 rule of three »educed thefe quantities to 14.6, or 14.4 per cent, of fulphur, contained in 

 fulphate of barytes ; a difference wholly to be neglefted. If, therefore we take 14.5 as the 

 average, for the quantity of fulphur contained in 100 parts of fulphate of barytes, we fliali 

 not be far from the truth. From the accordance of thefe experiments, repeated and varied, 

 I had nowno doubt, but concerning the fourcc where I was to feck the error, which gave 

 23.43 as the jufl: proportion. 



To afcertain this point, I operated in the following manner : I prepared fome lime, as 

 pure, I believe, as chymical means can procure it. I digefted white marble in muriatic 

 acid i and, by leaving an excefs of the earth, w.as certain, that by the fuperior affinity of 

 Hme for that acid, nothing clfe had been taken iip. Upon trying the folution with ammo- 

 nia, no precipitate took place. By means of carbonate of pot-afli, I feparated the lime in 

 the ftate of carbonate ; and, after well wafliing the precipitate, expofed it in a platina- 

 crucible to a violent heat, till the weight no longer diminiflied. I am acquainted with no 

 more efficacious method to prepare lime, fit for the delicate purpofes of fcientific chymiflry. 



One hundred parts of this lime were diffialvcd in dilute muriatic acid, in the fame platina- 

 crucible, previoufly weighed ; and then fulphuric acid was added in fufficient quantity. 

 Sulphate of lime was precipitated ; and the veflel was expofed to a heat, at firft gentle, to 

 evaporate the liquor ; and then, by degrees, raifed to a temperature, which could expel 

 every thing but the combined fulphuric acid, and leave the fulphate of lime completely 

 calcined. The crucible with the fait was then weighed, and the augmentation was 76. — < 

 It appears to me, that if we admit (and I fee no rcafon that we fliould not admit it) that 

 calcined lime and calcined fulphate of lime are wholly exempt from water, it muft be 

 clear, that the 76 additional weight were fulphuric acid ; and, that the fulphuric acid muft 



in 



