138 METALS AND THEIR COMBINATIONS. 



lime, forming calcium nitrate. This is dissolved in water, and to 

 the solution potassium carbonate (or chloride) is added, when calcium 

 carbonate (or chloride) and potassium nitrate are formed : 

 Ca(NO 3 ) 2 + K 2 CO 3 = 2KNO 3 + CaCO 3 



Large quantities of potassium nitrate are made also by decompos- 

 ing sodium nitrate (Chili saltpetre) by potassium chloride : 

 NaNO 3 + KC1 = KN0 3 -f NaCl. 



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

 about 3.8 parts of cold, and 0.4 part of boiling water. It has a cool- 

 ing, 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 manufacture 

 of guxywwder 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, CO 2 , N, SO^petcT) being formed, the sudden generation and 

 expansion of which cause the explosion. 



Potassium chlorate, Potassii chloras, KC1O 3 = 122.4 (Chlorate 

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

 solution of potassium hydroxide : 



6C1 + 6KOH == 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 hydroxide has been added : 



K 2 C0 3 + 6(Ca2OH) + 12C1 = 2KC1O 3 + CaCO 3 + 5CaCl 2 + 6H 2 O. 



Potassium chlorate crystallizes in white plates of a pearly lustre ; 

 it is soluble in 16.7 parts of cold, and 1.7 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 matter or other 

 deoxidizing agents, or with strong acids, which will liberate chloric 

 acid. When heated by itself, it is decomposed into potassium chloride 

 and oxygen. 



Potassium sulphate, Potassii sulphas, K 2 SO 4 174. Obtained 

 by the decomposition of potassium chloride, nitrate, or carbonate, by 

 sulphuric acid : 



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

 K 2 CO 3 + H 2 SO 4 = H 2 O + CO 3 



