XX DISSOCIATION 531 



" The vapour of the very dry trioxide was red, and on 

 cooling to +10 C. it condensed to a green liquid, which on 

 further cooling turned bright blue, showing that it was still 

 nitrogen trioxide. On allowing some nitrogen, dried by 

 passage through a long column of phosphoric oxide, to enter 

 the tube, the small amount of moisture it contained caused 

 rapid dissociation, and the resulting sudden increase blew 

 out the stopper of the tube." 



Five years' drying gave a liquid which, instead of becoming 

 olive-green above - 20 C., was permanently blue at ordinary 

 temperatures and perhaps consisted of undecomposed N 4 O 6 

 (Trans. Chem. Soc., 1912, 101, 2341). 



Influence of moisture on combustion. Baker's work on 

 dissociation formed part of an investigation initiated by 

 H. B. Dixon, on the influence of moisture on chemical 

 change and especially on combustion. The following 

 actions are checked, or altogether arrested, by careful 

 drying : 



2CO + O 2 -> 2CO 2 



C + O 2 -> CO 2 



S + O 2 ->6O 2 



P 4 +50 2 ->P 4 10 



2 H 2 + O 2 -> 2H 2 O 



A dried mixture of carbonic oxide and oxygen was sparked 

 without exploding (H. B. Dixon, Phil. Trans., 1884, 175, 

 630). Both sulphur and phosphorus were distilled to and fro 

 in sealed tubes containing dried oxygen without taking fire, 

 whilst purified carbon was only partially burned by prolonged 

 heating in oxygen (H. B. Baker, Phil. Trans., 1888, 179, 

 571). Hydrogen and oxygen were found to be almost 

 incapable of exploding when pure and dry (Baker, Trans. 

 Chem. Sac., 1902, 81, 400). 



The mixed gases, prepared by the electrolysis of purified 

 baryta, were passed through a column of phosphoric an- 

 hydride and collected in cleaned vacuous tubes of hard glass, 



