PHYSICAL AND LITERARYr 171 



fourth day, when their colour did hot fedm 

 to be altered. The water being now poured 

 off, was intirely infipid, and agreed in every 

 chemical trial with pure water. The • pow- 

 der, after being perfedly well dried, weighed 

 thirty feven grains. It did not diflblve intirely 

 in fpirit of vitriol ; but, after a brilk effer- 

 vefcence, part of it fubfided in the fame man- 

 ner as the calcarious earths, when mixed 

 with this acid. 



When I firft tried this experiment, I vvas 

 at the trouble of digefting the mixture in the 

 heat ofboiling water, and did not then know 

 that it would fucceed in the' heat of the 

 air. But Dr. AlJIon, who has, obliged the 

 world with many curious and ufeful difco- 

 veries on the fubjeft of quick-lime, having 

 had occafion to repeat it, I learned from him 

 that heat is not necelTary ; and he has more- 

 over added an ufeful purpofe to which this 

 property of magnefia may be applied j I mean 

 the fweetening of water at fea, with which 

 lime may have been mixed to prevent its pu- 

 trefaftion. 



That part of the dried powder which 

 does not diiTolve in fpirit of vitriol, confifls of 

 ^Jie lime feparated from the water. 



Quick-lime 



