xvii SULPHUR AND ITS COMPOUND 261 



10. What are sulphates ? Describe a method of preparation, and 

 give a short account of the appearance and properties of three 

 sulphates. 



11. How may sulphide of copper be obtained ? What differences 

 are there in the chemical nature, appearance, and properties of 

 sulphide of copper and sulphate of copper ? 



12. If iron and sulphur be heated and the product so obtained 

 treated with hydrochloric acid, what gas is obtained ? Give an ac- 

 count of its more characteristic properties. 



13. How could you prove that sulphuretted hydrogen contains 

 sulphur and hydrogen ? 



14. Sulphuretted hydrogen is passed through solutions of (1) copper 

 sulphate, (2) lead acetate. Describe what happens, and explain the 

 nature of the chemical changes. 



15. If in preparing hydrogen from iron and hydrochloric acid there 

 happened to be sulphide of iron mixed with the iron, with what 

 would the hydrogen be mixed, and how could you obtain this impurity 

 in a pure state ? 



16. What are "flowers" of sulphur and how is sulphur obtained 

 in this condition ? 



17. By what means may it be proved that sulphuretted hydrogen 

 contains its own volume of hydrogen ? 



18. What is meant by a double decomposition ? Give three 

 examples of such changes. 



19. What difference is there in the chemical behaviour of a 

 sulphite and a sulphate ? How would you detect the presence of 

 sodium sulphite in a quantity of sodium sulphate ? 



20. What do we mean by allotropic forms ? Give examples. 



