PHYSICAL AND LITERART. 207 



perfedly in the following part of the experi- 

 ment. I then mixed it with about twenty 

 ounces of pure water in a flafk, and, after al- 

 lowing the powder to fubfide, poured off the 

 water, which had all the qualities of lime- 

 water. And I fucceffively converted eight 

 waters more into lime-water, feven of thefe 

 in the fame quantity, and with the fame ma- 

 nagement, as the firft. The eighth was like- 

 ways in the fame quantity j but I allowed it 

 to remain with the chalk, and fhook it fre- 

 quently, for two days. This, after being fil- 

 trated, formed a cream or cruft upon its fur- 

 face when expofed to the air 5 changed the 

 colour of the juice of violets into green j fe- 

 parated an orange-coloured powder from a fo- 

 lution of corrofive fublimate j became turbid 

 upon the addition of an alkali •, was entirely 

 fweetened by magnefia j and appeared fo 

 ftrong to the tafte, that I could not have dif- 

 tinguiOied it from ordinary lime-water. And 

 when I threw fome fait ammoniac into the 

 lime which remained, the vapour of the vo- 

 latile alkali immediately arofe from the mix- 

 ture. 



■ In this experiment therefore the air is firft 

 driven out of the chalk by an acid, and then, 



in 



