216 Domestic Science 



,-, ,. volume of nitrogen . , . 



I he ratio ^ , - as determined from 



volume 01 oxygen 



the readings should agree fairly closely with that 

 obtained in the previous experiment. 



146. In Experiments 80 and 81 the action of .the 

 phosphorus and iron on the air resembles that of the 

 burning phosphorus, although in these experiments no 

 production of either heat or light will have been 

 noticed. In all three cases, what has occurred is that 

 the phosphorus (or iron) has united with a part of the 

 air, namely, the oxygen, and formed by combination 

 with this gas a new solid substance, which occupies a 

 very small volume compared with that of the gaseous 

 oxygen absorbed in its formation. Thus the white 

 powder formed when the phosphorus is burnt is called 

 " oxide of phosphorus ", and the brown powder (which 

 we usually call rust), produced by the action of moist 

 air on the iron, is termed " oxide of iron ". In Experi- 

 ments 79 and 80 the white oxide of phosphorus slowly 

 disappeared because it dis- 

 solved in the water present, 

 and in order to see more 

 clearly the nature of this 

 substance we will perform 



EXPERIMENT 82. Carefully 

 clean and dry a bell- jar, 



B, and a large glazed tile B 



(or plate), T. Dry a very 

 small piece of phosphorus 

 between filter-papers, and place 

 it on the middle of the tile 



(Fig. 69). Ignite it with a 



a j j F] S' 



warmed rod or wire and im- 

 mediately place the bell- jar over it. 



