chemical change by measurement of the gases evolved. 001 
By this method it therefore becomes possible to investigate 
the relation between the rate of evolution of a gas and the degree 
of supersaturation. 
It might be thought that a much simpler method of performing 
the work would be to supersaturate the solvent with the gas by 
means of pressure. The above method however gives at once a 
degree of supersaturation which otherwise could only be obtained 
by pressures up to 100 atmospheres and necessarily complicated 
apparatus. 
Fig. 8. 
Experimental method. 
The decomposition of diazobenzene chloride was investigated 
from this point of view. 
The rate of evolution of gas when the solution was stirred 
was ascertained as before. In another experiment a reaction 
mixture of the same composition was introduced into the vessel, 
and the solution vigorously stirred, so that only the normal satura- 
tion amount could be retained by the liquid. In about 20 seconds 
the motor was stopped, the vessel being immediately connected 
to the burette in which the gas given off is measured. At the 
end of the experiment when the evolution of gas had become very 
slow, the motor was again started, and the remaining excess of gas 
driven off. 
As the total amount of gas given off is thus known, the curve 
representing the evolution of gas can be plotted in conjunction with 
the curve obtained when the liquid was stirred. 
