SODIUM. 121 



QUESTIONS. 



181. How is potassium found in nature, and from what sources is the 

 chief supply of potassium salts obtained? 



182. What color have the salts of the alkali-metals, and which are 

 insoluble ? 



183. Mention two processes for making potassium hydrate, and what 

 are its properties ? 



184. Show by symbols the conversion of carbonate into bicarbonate 

 of potassium. 



185. Explain the principle of the manufacture of potassium nitrate, 

 and what is its action in gunpowder ? 



186. How is potassium chlorate made, and what are its properties? 



187. Give the processes for manufacturing iodide and bromide of 

 potassium, both in words and symbols. 



188. State the composition of potassium sulphate and sulphite. How 

 can they be obtained ? 



189. What is sulphuret of potash ? 



190. Mention tests for potassium compounds. 



20. SODIUM. 



Na 1 = 23. 



Occurrence in nature. Sodium is found very widely diffused 

 through all soils in small quantities. It occurs in large quanti- 

 ties in combination with chlorine, as rock-salt, or common salt, 

 which forms considerable deposits in some regions, or is dis- 

 solved in spring waters, and is by them carried to the rivers, 

 and finally to the ocean, which contains immense quantities of 

 sodium chloride. It is also found as nitrate, silicate, etc. 



Sodium and Sodium hydrate, Soda, NaHO = 40, may be obtained 

 lay the same processes mentioned for potassium and potassium 

 hydrate. 



Sodium chloride, Sodii chloridum, NaCl = 58.4 (Chloride of sodium, 

 Common salt}. This is the most important of all sodium com- 

 pounds, and is also the material from which the other com- 

 pounds are directly or indirectly obtained. Common table-salt 

 frequently contains small quantities of calcium and magnesium 

 chloride, the presence of which causes an absorption of mois- 



