584 Mr Lamplough, On the determination of the rate of 
This arrangement was found to be of the greatest possible assist- 
ance in conducting the experiments, for the reactions were always 
allowed to take place at atmospheric pressure to avoid all possi- 
bility of leak or change in the solubility of the gas, and it was 
therefore necessary throughout the experiments gradually to lower 
the tube L so as to keep the liquid in the two arms at the same 
level. 
In order to maintain the temperature of the gas in the burette 
the same as that in the reaction vessel, the former was provided 
with a water-jacket, and a current of water was passed first 
through the bath A, and then through the jacket of the burette. 
Some difficulty was experienced in maintaining this stream of 
water at a constant temperature, and it was found necessary to 
use a water cistern 0 provided with an overflow to keep the water 
at a constant level. Water was syphoned out from this cistern, 
passed through a copper tube, heated in a gas furnace, thence 
through a bottle containing the thermostat T , which regulated 
the supply of gas to the furnace, and then led into the water 
bath A. When working at a temperature of 60° to 70° it was 
found necessary to have further control over the temperature by 
means of a Bunsen burner, regulated by hand, under the water 
bath. 
Decomposition of Hydrogen Peroxide. 
For these experiments the stirrer and the inner surface of the 
vessel were completely covered with a coating of pure paraffin wax, 
so as to protect the solution from any effect which might be due 
to contact with the walls of the vessel, and all beakers, etc. in 
which titrations were performed were treated in the same way. 
Two experiments were conducted as follows: — 
Experiment I. A known volume of solution of hydrogen 
peroxide, whose strength had been determined by titration, was 
mixed with a known volume of a colloidal platinum solution at a 
given time. The mixture was at once poured into the reaction 
vessel and vigorously stirred for half a minute. After this short 
delay of known duration, measurement of the rate of evolution of 
oxygen was commenced. This measurement was continued until 
the rate was very slow, when the motor was stopped and the 
mixture poured into a large volume of dilute sulphuric acid and 
at once titrated. From this titration may be calculated the volume 
of oxygen which would have been evolved if the measurement 
could have been continued for an indefinite period. The total 
volume of oxygen which would be given off from the hydrogen 
peroxide solution can be calculated from the strength of the solu- 
tion, and hence the gas lost before measurement may be determined. 
