588 Mr Lamplough, On the determination of the rate of 
Temperature 60°. Temperature 67°. 
Volume, 
c.c. 
Time, 
minutes 
Velocity 
constant 
Volume, 
c.c. 
Time, 
minutes 
Velocity 
constant 
0 
o-oo 
0 
o-oo 
4 
0-43 
•147 
10 
0-41 
•317 
6 
0-66 
•149 
14 
0-59 
•330 
10 
1-21 
•148 
18 
0-80 
•358 
16 
2-27 
•149 
22 
1-09 
•335 
20 
3 -35 
•146 
28 
1-59 
•351 
23 
4-47 
•146 
32 
2-19 
•348 
26 
6-28 
•146 
36 
3-35 
•345 
28 
8-68 
•151 
38 
4-93 
•353 
29 
11-20 
•146 
38-7 
end-point, 
— 
29-6 
end-point, 
observed 
Mean T47 
observed 
Mean -345 
the rate of evolution of gas was calculated from the differences 
between successive observations given in the second column in each 
of the preceding tables, and the values so obtained were plotted 
with the amount of gas already evolved. 
The method of calculation adopted is most clearly described by 
an example. In the experiment performed at 44° '3 two successive 
observations were : 
40 c.c. 7 '93 min. 
50 c.c. 10-50 „ 
Thus 10 c.c. of gas were given off in 2 '57 min. and the rate of 
evolution of gas when 45 c.c. had been given off differed very little 
from 10/2-57, or 3'88 c.c. per min. 
It was found that in these experiments the observations were 
so accurate as to give very smooth curves when the rates of reaction 
were plotted in terms of the amount of gas already given off. 
As an example a table is given showing the results of calcu- 
lations made from the observations taken in the experiment 
performed at 44° "3 as given above. 
In Fig. 3 we have the result of plotting these calculated values 
with the amount of gas evolved. It will be seen that a straight 
line is obtained which cuts the line of zero rate of evolution of 
gas at 132 c.c. From this result it is obvious that the reaction 
is unimolecular throughout the range investigated, the rate of 
reaction being directly proportional to the amount of substance 
left undecomposed, if the end-point of the reaction is 132 c.c. 
When the value of the velocity constant K in the equation 
A 
