POTASSIUM, SODIUM, ETC. 129 



155. Potassium Carbonate. When wood ashes are 

 leached, potassium carbonate is the chief alkaline salt 

 extracted, and this product is called potash which, by 

 the removal of impurities, furnishes pure K 2 CO 3 . Potas- 

 sium carbonate is prepared from the chlorid in the same 

 way that sodium carbonate is prepared from its chlorid as 

 explained in Section 162. 



156. Potassium Chlorate is prepared by the action of 

 chlorin gas upon potassium hydrate. It is used in the 

 laboratory as an oxidizing agent, and for the preparation 

 of oxygen. It is one of the ingredients of safety matches. 



157. Potassium Sulfate is found in nature in the form 

 of double salts, in the Stassfurt deposits and elsewhere. 

 It is employed in the preparation of alum and other com- 

 pounds. There are two sulf ates of potassium : primary on 

 acid potassium sulfate, KHSO 4 , and secondary or normal 

 potassium sulfate, K 2 SO 4 . 



158. Miscellaneous Potassium Salts. Potassium 

 forms a large number of salts, as KC1, KBr, KF, KI, 

 KCN, K 2 O, K 2 S, KNO 2 , many of which are very valuable 

 in medicine, in the arts as photography, and in the labora- 

 tory for the preparation of other compounds. The salts 

 of potassium vary in chemical and physical properties 

 according to the acid elements or radicals with which the 

 potassium is combined. All of the common salts of 

 potassium, except the double silicates, are soluble in 

 water. 



159. Occurrence of Sodium. Sodium and potassium 

 are very much alike in general properties, and form analo- 



