84 PHYSIOGRAPHY. 



Nitre Nitrocalcite. 



NITRE. Prismatic Nitre-Salt. MOHS. 

 In capillary crystals and crusts.* 

 Lustre vitreous. Color white. Streak white. 

 Transparent . . . semi-transparent. 

 Sectile. Hardness =2-0. Sp. gr. =1-936. 

 Taste saline and cool. 



1. It dissolves very easily in water, is not altered on being exposed to 

 the air, and detonates with combustible .substances. 



2. Analysis. 

 By KLAPROTH. 



Nitrate of potash .... 42-55 

 Sulphate ^ .... 25-45 



Muriate > of lime .... 0-20 



Carbonate^ .... 30-40 



3. Nitre generally occurs in thin crusts on the surface of the earth, 

 sometimes upon limestone, chalk, or calcareous tufa; also in limestone 

 caves, and in sandstone. 



4' Spain, Italy and Hungary, afford considerable quantities of this 

 salt: in a higher state of purity, also, it is found in India. But especial- 

 ly in the United States, has it been found in large quantity, in limestone 

 caves in the south western states. In Madison county, Kentucky, there 

 is a cave 1936 feet long and 40 wide, which contains Nitre, intermingled 

 with earthy matter and nitrocalcite. One bushel of the earth affords 

 by lixiviation with wood ashes, from three to ten pounds of Nitre. It is 

 also met with, in the same vicinity, in loose masses, weighing several 

 pounds, or imbedded in sandstone. 



5. Its chief employment is in the production of gunpowder. 



NITROCALCITE. Calcareous Earthy-Salt. 



In efflorescent masses and silken tufts. 

 Color white or grey. 



* The artificial crystals are right rhombic prisms of 120, which com- 

 monly have the acute lateral edges and acute solid angles truncated. 

 Twin crystals are also common, the face of composition being parallel 

 with M. 



