contained In Sulphuric Acid. 1 15 



to prepare lime fit for the delicate purpofes of fcientlfic che- 

 miftry. 



One hundred parts of this lime were diffolved in dilute 

 muriatic acid, in the fame platina crucible, previoufly 

 weighed j 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 w'hich could 

 expel every thing but the combined fulphuric acid, and leave 

 the fulphatc 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 reafon that 

 we ihould not admit it) that calcined lime and calcined iul- 

 phate of lime are wholly ext-mpt from water, it muft be clear 

 that the 76 additional weight were fulphuric acid; and that 

 the fulphuric acid muft in^this (tate, more than in any other, 

 approach nearer to what may be termed abfolutely real acid. 

 One hundred parts of calcined falphate of lime contain, 

 therefore. 



Lime - - .57 



Sulphuric acid - 43 



100 

 Bv the former experiments (thofe made upon fulphur con- 

 verted into acid, and then united to barytes,) we had the 

 quantity of fulphur contained in fulphate of barytes. By the 

 latter (thoie made bv direftly combining lime with fulphuric 

 acid) we had the proportion of real acid contained in cal- 

 cined fulphate of lime. Confequently, by knowing the ratio 

 that fulphate of barytes bears to fulphate of lime, with regard 

 to the acid in each, we ftiall arrive at the knowledge of the 

 quantity of fulphur contained in real fulphuric acid. For 

 this purpofe, I attempted to diflblve, in water, 100 parts of 

 fulphate of lime. But finding in this method of proceeding 

 a confiderable inconvenience arifmg from the great quantity 

 of liquor neceflary to effe6l the folution of that fait, I had 

 recourfe to the following expedient: — Upon 100 grains of 

 calcined fulphate of lime, I poured fome oxalic acid, which 

 attracts the bafis with an afKnity fuperior to that exercifcd 

 by fulphuric acid. Oxalate of lime was here formed; but 

 oxahte of lime is foluble in a very fmall exccfs of any acid. 

 A little muriatic acid operated a complete folution ; and 

 thus a great quantity of fulphate of lime required but little 

 water to difTolve it. fnto this liquor, muriate of barytes 

 was poured, and fuffered to remain fome time, gently 

 heated. By thefe means any oxalate of barytes that might 

 have been formed, was retained in folution by the original 



il % excefs 



