PHYSICAL anp LITERARY. 219 
- mature and properties of this fubftance, 
which will probably be the fubject of my 
further inquiry. 
Ir is, perhaps, needlefs to mention here, 
that the calcarious fubitances ufed in ma- 
king the above experiments fhould be of 
the pureft kind, and burnt with the ur- 
moft violence of heat, if we would be fare 
of converting them into perfect quick lime. 
I therefore made ufe of chalk burnt ina 
{mall covered crucible with the fierceft fire 
of a black{mith’s forge, for halt an hour, 
and found it neceflary to employ, for this 
purpofe, a crucible of the Aufirian kind, 
which refemble black lead ; for, if any cals 
carious fubftance be heated to fuch a de- 
gree. in an ordinary or Heffian crucible, 
the whole of it is melted down, together 
with part of the veflel, into glafs. 
I now prepared to inquire into the pro- 
_ perties of the caultic alkali; in order to 
_ which, I made a cauftic or foap-ley in the 
_ following manner, 
TwekntTy fix ounces of very ftrong 
~ quick-lime made of chalk, were flaked or 
-Feduced to a fort of fluid patte, with eleven 
pounds 
