26 



T rftnsarfionf 



Art. V. — On the Velocity of Evolution of Oxygen from Bleaching-powder' 

 Solutions in Presence of Cobalt-nitrate, and the Modifications produced 

 by the Addition of various Compounds. 



By N. M. Bell, M.A., Canterbury College. 



[Bead before the Philosophical Institute of Canterbury, 2nd November, 1910.] 



In each experiment measurements of two kinds were made : — 



1. The evolved oxygen was collected in a burette and the volume read 

 at definite intervals. 



2. The evolved oxygen was calculated by titrating the bleaching-powder 

 with ^ arsenious acid before and after the experiment. The results of 

 the two methods agreed well. 



The concentrations obtained from the two titrations inserted in the 

 equation for a mono-molecular reaction gave the velocity. 



The reactions were carried out in a 100 c.c. glass flask, the rubber stopper 

 of which carried a short wide tube, conical at its lower part, and closed near 

 the bottom by a glass-rod stopper ground in. This rod stopper passed 

 through and was connected by a rubber-tube joint with a short glass guide- 

 tube carried by a cork at upper end of the outer glass tube. The accom- 

 panying diagram shows the complete apparatus. 



Lfivel 



Thermostat. 



The evolved gas was carried oil" by a narrow glass tube over a metre 

 long, arranged to condense and carry back into the flask any water-vapour 

 formed. The flask was charged with 25 c.c. of bleaching-powder solution, 



