600 Mr Lamplough, On the determination of the rate of 
Temperature 0° C. 
c.c. 
minutes 
c.c. 
minutes 
0 
0-13 
18 
2-97 
2 
0-28 
20 
3-72 
4 
0-45 
22 
4-67 
6 
0-64 
24 
5-97 
8 
0-89 
26 
7-92 
10 
1-18 
27 
9-46 
12 
1-51 
28 
11-70 
14 
1-92 
28-6 
14-10 
16 
2-41 
When the rates of reaction are calculated from these observa- 
tions, it is found that at first it is nearly bimolecular, but gradually 
changes so that towards the end of the reaction it is roughly uni- 
molecular in character. This fact does not simplify the problem, 
nor does it in any way lead to an explanation of the remarkably 
abrupt termination of the reaction when nickel carbonyl is present 
in excess. 
The rate of evolution of a gas from its supersaturated solution. 
It has been shown that the rate of evolution of a gas from 
a solution which is not agitated cannot be taken as a measure of 
the progress of a chemical reaction, and in fact that the rate 
of evolution is only indirectly dependent on the velocity of the 
reaction. 
By means of two experiments on the measurement of the 
gas evolved during a reaction, the manner in which the rate of 
evolution depends on the degree of supersaturation can be deter- 
mined. 
In Fig. 8 let OA and OB represent the progress of evolution 
of gas in the two experiments, OA being measured in the case 
where the solution was violently stirred, and OB without stirring. 
Then after the lapse of an interval of time OT, volumes of gas 
corresponding to aT and bT will be given off in the respective 
experiments. But the amount aT represents the total amount 
of gas which has been liberated during OT if the stirring is 
efficient, and therefore in the experiment without stirring, a 
volume of gas ab is stored up in the liquid. 
Hence the rate of evolution of gas at the point b is that 
corresponding to supersaturation of the liquid with a volume of 
gas ab. 
