[ 147 ] 



been in contad with the nitre. Hence in the experiments of Mr. 

 Hielm, on the quantities of charcoal of different woods requifite 

 to alkalize lOO parts of nitre, we find thefe quantities to bear 

 for the moft part fome analogy to their fpecific gravities, being ge- 

 nerally fmaller when the fpecific gravity of the charcoal is 

 lighter. 



Thus, :j:~ 



Grains requifite to alkalize I oo Grains of Nitre. 



Another circumftance of great importance towards procuring 

 jufl and uniform refults is, that the projedions of coal fhould 

 fucceed each other without delay as foon as the flame ceafes, for 

 as ignited nitre gives out pure air fpontaneoufly, and fo much 

 the more as it is more heated, the acid will be decompofed and 

 the nitre alkalized by a quantity of coal fo much the fmaller as 

 the intervals of projedion are longer. From inattention perhaps 

 to this and the laft mentioned particular, as well as from various 

 conditions of common charcoal, which feldom contains lefs than 

 tV and often -i- of its weight of moiflure and abforbed air, pro- 



T 2 ceeded 



t Schwed. Abliaiidl 17S1. p. 188. 



