[ 554 ] 
Gunpowder, a kind of that exploit ve Subftance, 
whofe Parts are highly rarefied in an intenfe and 
confined Heat, by which they readily explode in 
boiling Lye. * 
By this we may perceive, that the Difficulty in 
making Pot-afh aright, is, firft, to reduce the Mate- 
rials to Cinders and Afhes, and at the fame time to 
preferve their volatile, fulphurcous, and exhalable 
acid Parts, that are totally deftroycd in fuch a Degree 
of Heat ; and, fecondly, to calcine thefe Afhes dill 
further, fo as to flux their Salts, and vitrify their 
terreftrial Parts, and at the fame time to keep them 
feparate from each other, or prevent their running 
into an indiffolvable Glafs. To give Pot afh fome 
of thefe Properties, feems plainly to require a Degree 
of Heat that will totally deprive it of others. 
The moft likely Way by which it comes to re- 
ceive all thefe Properties, is from the Way of 
making it in Sweden above deferibed. In that Pro- 
cefs, the green Fir, in which the Afhes are burnt, 
impregnates them with the acid faline Parts of the 
Wood or Tar, which is well known to be in pretty 
large Quantities, and is abforbed and fixed by the 
alkaline Salts, and porous terreftrial Parts of the 
Afhes in this Procefs fo that, befides the fixed al- 
kaline Salts of the Afhes, the Pot-afh, thus made, 
muft likewife contain the more volatile Salts of the 
Pine, which are exhaled in Smoke by burning the 
Pine alone in the open Air. Befides thefe, it like- 
wife contains the refinous Parts and fulphureous 
Fumes of the Pine, that are hindered from exhaling 
by the Heap of the Mafs. 
