[ 274 ] 



though 125 are faid to be fufficient. Dojfic Elab. laid open no, 

 1 Labor, in Gro/s 68, in note per WeigUb. and in effcdt 125 grains- 

 chalk, at the above rate, would furnifh 52 grains of fixed air, 

 which would faturate 2^ of vol-alkali, and the ammoniac contains a 

 fufEciency of water. 



Hence alfo we fee how it happens that 100 parts fal ammo- 

 niac decompofed by 200 parts chalk frequently afford 89, nay, ac- 

 cording to Baume, even 94 parts aerated vol-alkali, for if there 

 were no lofs 125 parts of chalk were fuiEcient, but then this large 

 quantity of fixed air is expelled, not by the acid of the fal ammo- 

 niac, but by the heat applied, as Pellitier de la Sale has no- 

 ticed, 2 Pharmacopie de Londres 427, and on this account mag- 

 nefia, as it parts with its fixed air much more eafily, and con- 

 tains more water, affords a quantity of aerated vol-alkali, when 

 ufed as a medium for decompofing fal ammoniac, nearly double 

 that of the fal ammoniac employed. Thus VVeflrumb from roo 

 grains of fublimed fal ammoniac and 300 of magnefia obtained 

 193 grains aerated vol-alkali, a Chy. An. 17S8, p- i 5 ; his magnefia 

 mufl have contained a very large proportion both of fixed air 

 and water, for he fays that 1920 grains of it being calcined left 

 only 600 of earth, ibid. 17. 



Hence alfo, Dolfuz having treated loo parts fal ammoniac with 

 125, and even with 200 of chalk, in a glafs retort, obtained no 

 more than 50 of aerated vol-alkali ; the fame thing happened when 



he 



