Chap. 9.] ' . Ponderous Earth. 49 



earth, or lime, is foluble in a fmall proportion in water, 

 with which it contra&s great heat. It is infufible with- 

 out addition. It .attracls the carbonic -acid from the 

 fixed alkalies, and by itfelf becoming mild renders 

 them cauftic. Its fpecific gravity is 2,723. ' 



Magnefia does not burn into a cauftic fabftance like 

 quick-lime, though it is deprived of its carbonic acid 

 by the application of heat. It is foluble in feverai 

 acids, and forms with the vitriolic the fal catharticus- 

 amarus, or Epfom fait. When mixed with water, ic 

 fhews a very fmall degree of heat, but without any 

 effervefcence. It requires 7,692 times its weight of 

 water for its folution. It is not precipitated from 

 other acids by the vitriolic, as calcareous earth is. Its 

 fpecific gravity is 2,155. 



Baryies is by far the mofl ponderous of the earths> 

 from which circurnflance it derives its name. 



With vitriolic acid it forms the ponderous fpar, 

 which is infoluble in water ; and its combinations with 

 the nitrous and muriatic acids are alfo not very folu- 

 bkj but with the acetous acid (or vinegar) it becomes 

 deliquefcent. Combined with carbonic acid, it is fo- 

 luble in 1550 times its weight of water, when pure in 

 900 times. The fpecimens of barytes naturally com- 

 bined with carbonic acid are rare ; it is more com- 

 monly found united with the vitriolic acid. From 

 this the earth may be frparated by the following pro- 

 eels : Pound the ponderous fpar, and mix it with twice 

 its weight of fixed alkali > expofe this mixture to a 

 ftrong red heat for about two hours. The acid quits 

 the earth to unite with the alkali, forming a neutral 

 fait, which may be waftied away. The earth remains 

 combined with carbonic acid, which may be difpellerl 

 by heat. The fpecific gravity of this earth, when 

 pure, is 3,775, 



VOL. II. E ArgUl, 



