ACTION OF LIGHT ON THE HTBEACIDS OF HALOGENS. 



91 



position takes place in rays considerably below the bine. How far this is 

 due to beating effect has yet to be proved ; an apparatus is being pre- 

 pared to stndy with greater accuracy the influence of different parts of 

 the spectrum on chlorine water and on hydrochloric acid and oxygen. 



The influence of oxygen on a mixture of chlorine and hydrogen has 

 been observed ; the gases were exposed for periods varying from three 

 hours to three days. At first it was found that, with increased ex- 

 posure, the amount of free chlorine was reduced ; but when all the hydro- 

 gen present had been converted into hydrochloric acid the green colour of 

 the chlorine gradually returned, owing to the slow decomposition of the 

 acid by the oxygen. Analysis gave — ■ 



After three hours' exposure, 41-2 per cent, free chlorine. 

 „ five „ „ 311 „ „ 



,, D'^y ,, ,, 



20-3 

 ,, oi y <• 5, 



seven „ 

 two days' 

 three ,, 



Little has been done on the oxidation of the other halogens. We 

 hope, however, to be able to report on these when the Association meets 

 next year. 



Table I. — Decomposition of Gaseous Eydrochloric Acid and Oxygen in 

 Sunlight after 170 days' exposure, from December 9 to May 26. 



