342 MURIATES. 



springs, near Sasso, in the territory of Florence, and also in Vol- 

 cano, one of the Lipari islands. 



Genus II.— CARBONATES. 



Sf>. 1. Natron. — Nitrum, Plin. Hist. Nat. xxi. p. 46.-— The 

 native carbonate of soda, or natron, of which there are two spe- 

 cies, the common and the radiated, is found abundantly in various 

 parts of the world, particularly in Hungary, and in Egypt. It 

 occurs forming an efflorescence on the surface of the soil, or on 

 certain rocks; it is also found on the bottoms and sides of lakes 

 that become dry in summer. In Hungary, according to Ruckert 

 and Parmand, there are so many natron lakes, that 50,000 quintals 

 of soda could be obtained from them annually. Its colours are 

 yellowish and greyish-white. When compact, the structure is 

 granular or radiated, and the lustre vitreous; by exposure to the 

 weather it becomes dull, friable, and opaque. It is largely em- 

 ployed in the manufacture of glass and soap, and when separated 

 from impurities by lixiviation and crystalization, it is used in medi- 

 cine as an antacid. 



Genus III.— MURIATES. 



Sp. 1. Rock-Salt. — Common Salt. — This substance is found 

 in a solid state, forming, in some places, immense beds, and in 

 others large mountains. Its most common colours are white and 

 grey ; it also occurs of various shades of red, yellow, brown, blue, 

 and green. It varies from transparent and translucent to opaque . 

 the lustre is shining and vitreous ; it occurs massive, disseminated 

 in crusts, stalactitical, and crystalized in cubes and octahedrons. 

 The structure is indistinctly laminar, it is rather brittle, and easily 

 frangible. The specific gravity is 2-14. It yields easily to 

 the knife. When exposed to the air, it slowly deliquesces. The 



