Analyfts of the Air. 1 87 



of vegetables are fee to cryftallize, it is 

 needful to take off the skin or Pellicle, 

 which covers the liquor, before the falts 

 will (hoot well. 



We fee from the great quantity of air, 

 which is found in falts, of what ufe it is 

 in their cryftallization and formation; and 

 particularly, how neceffary it is in making 

 falt-petre from the mixture of falc of tartar, 

 and fpirit of nitre. For fince, by Experiment 

 72 and 73, a great deal of air flies away, in 

 the making of Sal Tartar, either from nitre 

 and tartar, or from tartar alone ; it mud 

 needs be neceflary, in order to the forming 

 of nitre from the mixture of Sal Tartar and 

 fpirit of nitre, tha: more air mould be in- 

 corporated with it, than it contained either 

 in the Sal Tartar or fpirit of nitre. 



Experiment LXXV. 



Near half acubickinch of compound Aqua- 

 fortis, which bubbled, and made a con- 

 fiderable expanfion in diftillation, was fbon 

 diftilled off: as it cooled, the expanfion 

 abated very faftj and a little air was abforb- 

 ed. Whence it is evident, that the air ge- 

 nerated by the diftillation of nitre, did not 

 arile from the volatile fpirituous particles. 



Hence 



