ALUMINIUM. MAGNESIUM AND ZINC. 239 



than lead. It is cheaper than copper. It is not affected 

 by air and water as readily as iron. Zinc melts at 412, 

 and boils at 1040. At a still higher heat it may be dis- 

 tilled. So-called galvanized iron is merely sheet iron coated 

 with zinc. 



QUESTIONS. 



308. What is said of barium and strontium compounds ? 309. Describe 

 an experiment in which strontium nitrate is used. 310. Where and how 

 does calcium occur in nature? What is quicklime? What is said of al- 

 kaline earths? What of the caustic power of lime? 311. Explain the 

 manufacture of quicklime. How does heat effect this decomposition ? 

 312. Illustrate the attraction of lime for water, and for carbonic anhy- 

 dride. 313. What is stated as to the solubility of lime? To what uses is 

 lime-water applied? 314. What are the ingredients of mortar? What 

 chemical changes occur in mortar as it hardens and dries ? 315. Under 

 what forms is carbonate of calcium found ? Mention some animals which 

 furnish it.-*-316. Explain the deposition of carbonate of calcium from 

 natural waters. 317. What are stalactites? What stalagmites? Where 

 found? How formed? 318. What is said of calcium carbonate in the 

 sea? 319. What is gypsum? How is plaster made? Explain the "set- 

 ting" of plaster. 320. How may casts of medals be made? 321. De- 

 scribe the mutual reactions of sulphate of calcium and carbonate of am- 

 monium under different circumstances. 322. How is chloride of lime used 

 in bleaching ? 323. Of what is it composed ? How made ? 324. How 

 does calcium phosphate occur in nature ? 325. What are the properties of 

 aluminium ? 326. What is clay ? Name some precious stones containing 

 alumina. 327. Of what is common alum composed? How is it used in 

 dyeing? What is a mordant ? 328. Name some other alums. 329. What 

 are the properties of magnesium ? What is Epsom-salt ? 330. Name 

 some of the rare earths occurring in precious stones. 331. How is zinc 

 obtained? What is "philosopher's wool?" 332 and 333. What is said 

 of the salts of zinc ? 334. What of its uses ? 



