EXERCISES 109 



2. Look up the densities of the following metals: sodium, alu- 

 minum, iron, lead, gold. Is sodium heavier than water? 



3. Bromine is an element similar to chlorine. Give the name of the 

 compound it forms with sodium,. with hydrogen, with carbon, and 

 with sulphur. 



4. When a jet of hydrogen issuing from a glass tube is first lighted, 

 its flame is colorless and invisible; but when the glass becomes hot, the 

 flame is yellow. What element forms a part of glass? 



5. When common salt is treated with concentrated sulphuric acid, 

 hydrogen chloride is formed. Where does its hydrogen come from? 

 Its chlorine? 



6. What compounds are formed when carbon disulphide burns? 



7. When a ton of soft coal is heated, it gives off about 6 Ibs. of 

 ammonia. What elements must coal contain? 



