298 CHEMICAL MANURES. 



away from Stassfurt the factories of Aschersleben at Bienenburg, of 

 Thiederhall in Brunswick, the Solvay factories at Bernburg, and the 

 Wilhelmshall pit near Anderbeck in the neighbourhood of Halber- 

 stadt. It would be futile to study here in detail the potash salt 

 deposits of Stassfurt and elsewhere. The reader desirous of more 

 ample information need only consult the special treatises on the 

 subject. But as a knowledge of the manufacturing methods about 

 to be described presupposes a knowledge of the minerals which 

 enter into the composition of crude potash salts, it is deemed useful 

 to describe them briefly. 



Crude Potash Salts. — 1. Carnallite forms the chief ingredient 

 of crude potash salts. In the pure state it is clear as crystal, often- 

 iridescent ; generally however it is coloured red or reddish-brown by 

 scales of crystallized oxide of iron. Its fracture is conchoidal, 

 density 1-65. It is rarely found in distinct crystals in nature. 

 Carnallite crystallizes in the rhombic system. The angles of the 

 bases are 120° and 60°. The crystals of secondary formation met 

 with in mines rarely have a tablet form. They are more often 

 octahedral. Sometimes great masses of carnallite crystals are found 

 so compressed by pressure that their surfaces appear concave ; the 

 crystalline form is, however, quite distinct. Pure carnallite responds, 

 to the formula KCl + MgCl.j + 6H^0, and contains : — 



TABLE XCY.— ANALYSIS OF CAEXALLITE. 



Per cent. 

 Potassium chloride . . . • . . .26*76 

 Magnesium ,, . . . . . . • 34- 50 



Water 38-74 



100-00 



100 parts of water at 18-75° C. (66-75° F.) dissolve 64*5 parts. 



2. Sylvine or Sylvmite is a natural product resulting from the 

 decomposition of carnallite, and consists mostly of pure potassium 

 chloride. Freed from the common salt with which it is mixed, it. 

 has the composition represented by the formula KCl, and contains 

 in the pure state : — 



TABLE XCVL— ANALYSIS OF SYLYINITE (PURE). 



Per cent. 



Chlorine 47-58 



Potassium . . . • . • • .52-42 



100-00 



It is often colourless, rarely reddish or brown, brilliant like glass^ 

 with slightly conchoidal reflection, altogether resembling rock salt, 

 crystallizing like the latter in regular cubes with an octahedral 

 surface. Its fracture is angular, its density is 2-025. The potash 

 salt found at Kalusz consists chiefly of sylvine ; it is coloured blue. 



