QUESTIONS AND PROBLEMS 133 



and chemical properties of iron. What is steel, and how is it 

 tempered ? In the conversion of impure iron into steel by the 

 Bessemer process how is phosphorus eliminated ? 



217. How may ferrous sulphate be prepared from metallic iron? Give 



the formula of the crystallised salt. How may ferric sulphate be 

 obtained from ferrous sulphate ? Illustrate by equations. 



218. Similarly describe how ferrous and ferric chloride may be prepared. 



What is the difference in colour between soluble ferrous and ferric 

 salts ? 



219. How may ferrous and ferric oxide be respectively obtained from 



soluble ferrous and ferric salts ? State also how ferric oxide may 

 be prepared from (i) metalhc iron, (2) ferrous oxide, and (3) ferric 

 carbonate. 



220. How may ferrous sulphide be prepared (i) from metallic iron and 



(2) from a soluble ferrous salt? Explain the action of dilute 

 acids upon ferrous sulphide. 



5, Manganese. 



221. Name one of the principal ores of manganese. 



222. Mention three oxides of manganese, and state whether all are basic. 



If not, state which is the basic and which the acidic oxide of the 

 three. 



223. Which of the oxides yield oxygen on heating, and act as oxidising 



agents? What is the action of each on hydrochloric acid? 

  Illustrate by equations. 



224. Express the composition of potassium permanganate by a formula, 



and state how much '* available " oxygen it possesses when acting 

 as an oxidising agent. 



6. Aluminium, 



225. How does aluminium occur in nature ? 



226. Describe the chemical and physical properties of the metal. 



227. How does alumina occur in nature, and how can it be prepared 



from alum ? How is alumina distinguished from the other basic 

 oxides met with in agriculture ? 



228. Judging from the analogous production of a sulphate from a carbonate, 



how should it be possible to prepare aluminium sulphate from 

 the silicate ? What is alum, and how may it be prepared from 

 aluminium sulphate ? Illustrate by equations. 



229. Name some of the principal silicates of aluminium occurring in 



nature. What property does this salt possess that renders it of 

 value in pottery making? What is essentially the chemical 

 change in the burning of bricks ? 



