34-36] 



PREPARATION OF NITROGEN 



15 



of the gas, as shown in fig. 16. It will burn brilliantly. 

 When the sulphur has ceased burning withdraw the de- 

 flagrating spoon and pour a little water coloured with a few 

 drops of blue litmus solution into the bottle. The sulphur 

 dioxide formed by the combination of the sulphur with the 

 oxygen will be dissolved, and the litmus will be turned red, 

 showing that an acid body has been formed. 



34. Burning Charcoal in Oxygen.— Place a piece 

 of charcoal in a clean spoon and burn it in a jar of oxygen, 

 just as the sulphur was burned in the last experiment. It 

 will glow brightly but will give no flame. After all burning 

 has ceased pour lime-water into the jar and shake up. The 

 lime-water will turn milky owing to the presence of carbon 

 dioxide, which is formed when charcoal is burned in 

 oxygen. The action of carbon dioxide on lime-water is 

 the more fully explained in paragraph 42. 



Preparation and Properties of Nitrogen 



35. The most convenient source of nitrogen is the air, 

 which consists chiefly of a mixture of the two gases oxygen 

 and nitrogen in the proportion of four volumes of the latter to 

 one of the former. To prepare nitrogen 

 it is only necessary, then, to remove 

 the oxygen from a portion of the air. 



36. Experiment. — Half fill a stone- 

 ware dish with water and float on its 

 surface a small evaporating dish. In 

 the dish place a piece of phosphorus 

 about the size of a pea. Care must 

 be taken not to ignite the phosphorus. 

 It should be cut under water and dried ^Jg 

 as rapidly as possible by means of 

 filter-paper. Next place a stoppered 

 bell-jar over the basin, as shown in figure 17. Ignite the 

 phosphorus by touching it with a hot wire. Quickly withdraw 



