Intensity of Rays of High Ref Tangibility . 



281 



opened, and by blowing air in at the side tube J a measured 

 volume of acid was caused to rise in E, thus forcing an equal 

 volume of air into A. Chlorine being expelled at C ; C and 

 D were then closed, and, after the gas had thoroughly mixed, 

 the tubes were again exposed to light of the same intensity 

 as in the first case : this process was repeated until all the 

 chlorine was replaced by air. Knowing the capacity of A 

 and the proportion of air introduced at each operation, the 

 amount of chlorine could be calculated. Two series of ex- 

 periments were made under different conditions of light, the 

 intensity for each series remaining nearly constant. The 

 results are given in the next table. 







First Series* 





No. 



Expansion of CI 

 in centim. 



Per cent, of 

 CI in gas. 



Expansion of CI 

 in actinometer. 



Corresponding 



intensity of light 



(unit = 1). 



1. 



265 



100 



80 



•1107 



2. 



14-5 



63-7 



7-9 



•1092 



3. 



9-25 



41-0 



17-9 



•1092 



4. 



5-25 



261 



179 



•1092 



5. 



475 



7-1 



7-9 



•1092 



6. 



2-0 



2-0 



7-9 



•1092 



7. 



0-5 



05 



7-95 



•1100 



8. 



0<l 



01 



7-9 



•1092 



Second Series. 



No. 



Expansion of 01 

 in centim. 



Per cent, of 

 CI in gas. 



Expansion of Cl 

 in actinometer. 



Corresponding 



intensity of light 



(unit =1). 



1. 



11*7 



100 



355 



•0491 



2. 



625 



63-7 



35 



•0484 



3. 



595 



410 



35 



•0484 



4. 



435 



11-3 



3-3 



-0456 



5. 



1-0 



3-0 



22 



•0304 



6. 



0-15 



0-8 



34 



•0466 



It is seen from the double nature of the curve, fig. 5, Plate 

 III., that the first effect of dilution is very marked, diminish- 

 ing after a time, and finally increasing when only a small 

 per cent, of chlorine remains in the tube. It was found, 

 however, that chlorine was gradually given off (from the 

 sulphuric acid which was saturated with the gas) to such an 

 extent that, after complete expulsion of the chlorine by air, 



Phil. Mag. S. 5. Vol. 32. No. 196. Sept. 1891. U 



