580 Mr Lamplough, On the determination of the rate of 
On the determination of the rate of chemical change hy measure- 
ment of the gases evolved. By F. E. Everard Lamplough, M.A., 
Trinity College. 
\Read 18 May 1908.] 
The evolution of a gas from a homogeneous liquid is a common 
phenomenon. In some cases the gas may have been stored in the 
liquid at a lower temperature or higher pressure, as in the evolu- 
tion of carbon dioxide from aerated liquids, whilst in many other 
cases the gas is the result of a chemical action. 
When a gas is given off as a product of a chemical action which 
occupies a measureable time, it might be supposed that when time 
has been allowed for the supersaturation of the liquid by the gas, 
the further rate of evolution of the gas would be a measure of 
the progress of the chemical change. This would be expected 
especially in those cases where very sparingly soluble gases result 
from the chemical action. Accordingly it is not surprising that 
when chemists began to investigate the dynamics of chemical 
actions, a measurement of the evolution of gas produced during 
a change was often used to determine the course of the reaction. 
Of the researches which have been prosecuted by this method, 
special reference will be made to the work of Veley, Hantzsch, 
and Cain and Nicoll. 
By the introduction of solid substances into a liquid super- 
saturated with gas, the rate of the evolution of the gas is enormously 
increased ; agitation of the liquid brings about the same result. 
This influence of solid particles on the rate of evolution of gases 
during chemical action has been especially studied by Veley, Phil. 
Trans. 1888, 257. It was found that the rate of evolution of gases 
during the progress of many chemical actions was greatly increased 
by the presence of inert substances such as silica, graphite, pumice 
and powdered glass. 
On the other hand the comparative effect of agitation of the 
reacting liquids seems to have received little attention. It will 
however be shown that when a gas is formed during a reaction in 
homogeneous solution the liquid becomes highly^ supersaturated 
with the gas, and this storing up of the gas makes it impossible 
to investigate the rate of reaction by measurement of the rate of 
evolution of gas unless sufficient means are taken to prevent any 
supersaturation. 
In the paper referred to, Veley came to the conclusion that the 
presence of silica, pumice and graphite increases the rate of evolu- 
tion of gas because the velocity of reaction is increased by the 
