QUESTIONS AND PROBLEMS 131 



The Metals and their Salts. 

 I. Potasshun and Sodhnn. 



188. Mention the principal compounds of potassium and sodium occurring 



in nature. 



189. Describe the principal physical and chemical properties of the two 



metals, pointing out how they are distinguished from other metals, 

 and how they differ from each other. 



190. Suggest a method for preparing the hydroxides (i) from the metals, 



(2) from the carbonates. Can the oxides be obtained from the 

 hydroxides by heating? 



191. Represent the composition of the carbonates and bicarbonates by 



formulae. How may the latter be prepared from the former ? 

 Calculate the percentage loss in weight when the bicarbonates are 

 heated. Name one of the principal sources of carbonate of 

 potassium. 



192. Mention some of the principal sources of common salt. Illustrate 



its crystalline form by a drawing. How may chloride of potassium 

 be obtained from carnallite ? Are the crystalline chlorides of 

 potassium and sodium hydrated or anhydrous salts ? 



193. How may the sulphates of potassium and sodium be prepared from 



(i) the metals, (2) the hydroxides, (3) the carbonates, (4) the 

 chlorides, (5) the sulphites, and (6) the nitrates? Represent each 

 reaction by an equation. Represent the composition of Glauber's 

 salt by a formula. 



194. What are the principal natural sources of the nitrates of potassium 



and sodium ? Give several methods for their artificial preparation. 

 State the principal uses to which these two nitrates are put. 



195. Give formulae for the three phosphates of potassium and sodium, and 



state how each could be prepared. 



196. How is soluble glass prepared, and of what does it consist? In 



what respect does glass containing sodium silicate differ from 

 glass containing potassium silicate ? 



197. By what test may the salts of potassium and sodium be distinguished 



from each other, and from the salts of all other metals ? 



198. In respect to the solubility of their salts, how are the metals of the 



alkalies distinguished from the metals of all other groups? 



2. Calcium. 



199. Name the most abundant compounds of calcium occurring in nature. 



200. How is the metal calcium distinguished in its chemical properties 



from the metals potassium and sodium, and magnesium and zinc ? 



201. How are the oxide and hydroxide of calcium prepared on the large 



