\, [ 266 ] 



ift. For want of a due eflimate of the quantity of mere vol- 

 alkali in a 2;iven quantity of aerated alkali, the fubflance to be fa- 

 turated with the three other mineral acids. Dr. Prieftly's experi- 

 ments, the bafis of the eftimate I then formed, not exhibiting the 

 temperature and prefTure of the atmofphere when the volumes of 

 fixed and alkaline airs were combined, afforded an opportunity for 

 forming rather an approximation than an accurate determination of 

 their feveral weights. 



2d. I WAS not then aware of the difficulty of finding the exadl 

 point of faturation of the aerated vol-alkali with the mineral acids ; 

 a difficulty however mentioned by Macquer *, and fo great that 

 Du Hamel judged it impoffible to vanquifli it f. Wenzel very fa- 

 gacioufly abforbed the excefs of acid by oyfler fhells, but in my 

 mode of experimenting this teft could not be applied ; hence there 

 was an excefs of acid in all of them. Thefe errors induced me to 

 analyze rather than compofe thefe falts. 



Of Aerated Vol-Alkali. 



By diftilling 100 grains of aerated vol-alkali with 300 of dry 

 flacked lime in a pneumatic apparatus and a fand heat I obtained 

 129 cubic inches of alkaline air, barometer 30,2, and thermometer 



at 



» Macquer's Elem. 389, Englifli. f Mem. Par. 1735, p. 664, in &vo. 



