130 CHEMISTRY. 



water. What is electrolysis ? 142. Explain the process of obtaining hydro- 

 gen by decomposing water by means of red-hot iron. What reaction takes 

 place? How does this experiment illustrate decomposition and composition ? 

 143. Give in full the best method of preparing hydrogen gas. Give the ex- 

 planation of the chemical reaction. 144. Under what circumstances will 

 oxygen and hydrogen unite ? How is a eudiometer used ? 145. How does 

 the specific gravity of hydrogen compare with that of other substances ? Ex- 

 plain the table. 146. Give the contrast between hydrogen and carbonic an- 

 hydride. How is hydrogen transferred from one jar to another? 147. 

 What is said of ballooning ? When should balloons be used ? 148. What 

 is hydrogen in relation to combustion ? Explain the ' ' philosopher's candle. " 

 What caution is needed to prevent explosion ? 149. Describe the experi- 

 ment represented in Fig. 42. 150. How may it be shown that hydrogen is 

 not a supporter of combustion ? 151. Describe and explain the effects pro- 

 duced by burning hydrogen in glass tubes. 152. What is said of breathing 

 hydrogen? 153. What of sounds produced in this gas? 154. What is the 

 composition of illuminating gas ? What is the fire-damp of coal-mines ? 

 What is marsh gas ? Describe the mode of collecting it represented in 

 Fig. 46. How is it freed from the carbonic anhydride that is mingled with 

 if? Describe the experiment represented in Fig. 47. To what is the 

 brightness of illuminating gas owing ? 155. What is said of hydrogen per- 

 oxide ? 156. State in full what is said of the nature of hydrogen ? 157. 

 State and illustrate the differences between compounds and mixtures. 

 158. What is said of the extent of the chemical agency of water ? Mention 

 some of the ways in which this agency is exerted. 159. What is meant by 

 water of crystallization ? Give examples. What is efflorescence ? What 

 deliquescence ? How is water of crystallization usually expressed in form- 

 ulae ? 160. \Vhat is ammonia ? Where does it occur ? Whence its name ? 

 161. Explain its production. 162. Describe the preparation of ammonia. 

 Write the equation. 163. What is said of the solution of ammonia in wa- 

 ter? 164. What is cyanogen ? What is meant by a radical ? 165. How 

 is cyanogen obtained? 166. What are the properties of hydrocyanic 

 acid? 



