132 CHEMISTRY FOR AGRICULTURAL STUDENTS 



scale? Compare the solubility of the hydroxide with that of 

 caustic soda and magnesia. What purpose does the lime serve 

 in mortar and hydraulic cement? 



202. Name the principal natural forms of calcium carbonate. How may 



the carbonate be produced by precipitation from ( i ) lime water 

 and (2) chloride of calcium solution ? What evidence is there of 

 the existence of a bicarbonate of calcium ? Give two methods for 

 softening water containing the dissolved bicarbonate. Illustrate 

 by equations. 



203. Describe a method for producing chloride of calcium. Name its 



characteristic property, and state for what purpose it may there- 

 fore be used. 



204. How does sulphate of calcium occur in nature ? How is plaster of 



Paris prepared, and what is the explanation of its use as a plaster ? 

 Compare the solubility of sulphate of calcium with that of the 

 sulphates of sodium and magnesium. When water is permanently 

 hard with calcium sulphate, how may it be softened ? Illustrate 

 by equations. 



205. Name some of the natural sources of calcium phosphate. Explain 



the action of acids, e.g. hydrochloric, sulphuric, and phosphoric 

 acid, upon calcium phosphate, expressing the reaction by 

 equations. What is "superphosphate of lime"? What is the 

 action of chalk on superphosphate ? 



206. Give some methods for the preparation of calcium silicate. Explain 



the solubility of freshly precipitated calcium silicate in dilute 

 acids. Is calcium silicate a fusible salt ? 



207. Name a test by which calcium salts may be distinguished. 



3. Magnesium. 



208. Name the principal natural sources of magnesium, and describe the 



physical and chemical properties of the metal. 



209. How may magnesia be prepared (i) from the metal, (2) from the 



carbonate, {3) from any soluble salt ? Describe its properties. 



210. How may magnesium carbonate be prepared ? 



211. What is the distinctive property of magnesium chloride? 



212. Give the formula for Epsom salt, and name the salt of another 



metal with which it is isomorphous. 



213. Name some naturally occurring silicates of magnesium. 



214. By what test may soluble magnesium salts be identified? 



4. Iron. 



215. Name the principal ores of the metal iron. 



216. How may the metal be isolated from its oxide? Give the physical 



