118 METALS AND THEIR COMBINATIONS. 



Large quantities of potassium nitrate are also made by de- 

 composing sodium nitrate (Chili saltpetre) by potassium chloride: 



Na]SrO 3 + KC1 = KN0 3 + NaCl. 



Potassium nitrate crystallizes in six-sided prisms; it is soluble 

 in about 5 parts of cold, and 0.5 part of boiling water. It has 

 a cooling, saline, and pungent taste, and a neutral reaction. 

 "When heated with deoxidizing agents or combustible substances, 

 these are readily oxidized. 



It is this oxidizing power which is made use of in the manu- 

 facture of gunpowder an intimate mixture of potassium nitrate, 

 sulphur, and carbon. Upon heating or igniting the gunpowder, 

 the sulphur and carbon are oxidized, a considerable quantity of 

 various gases (CO, C0 2 , 1ST, SO 2 , etc.) being formed, the sudden 

 generation and expansion of which cause the explosion. 



Potassium chlorate, Potassii chloras, KC10 3 = 122.4 (Chlorate of 

 potassium), may be obtained by the action of chlorine on a boil- 

 ing solution of potassium hydrate : 



601 + 6KHO = 5KC1 + KC1O 3 + 3H 2 O. 



A cheaper process for the manufacture of potassium chlorate 

 is the action of chlorine upon a boiling solution of potassium 

 carbonate, to which calcium hydrate has been added: 



K 2 CO 3 + 6(Ca2HO) -f 12C1 = 2KC10 3 + CaCO 3 + 5CaCl 2 + 6H 2 O. 



Potassium chlorate crystallizes in plates of a pearly lustre; 

 it is soluble in 17 parts of cold, and 2 parts of boiling water. It 

 is even a stronger oxidizing agent than potassium nitrate, for 

 which reason care must be taken in mixing it with organic or 

 other deoxidizing agents, or with strong acids, which will lib- 

 erate chloric acid. When heated by itself, it is decomposed into 

 potassium chloride and oxygen. 



Potassium sulphate, Potassii sulphas, K 2 S0 4 = 174. Obtained 

 by the decomposition of potassium chloride, nitrate, or carbon- 

 ate, by sulphuric acid : 



2KC1 + H 2 SO 4 = 2HC1 + K 2 SO 4 ; 

 K 2 C0 3 + H a S0 4 = H 2 O + CO 2 + K 2 S0 4 . 



