586 Mr Lamplough, On the determination of the rate of 
Decomposition of Diazobenzene Chloride. 
This subject had previously been investigated by many workers, 
among whom may especially be mentioned Hantzsch (. Ber . 1900, 
xxxiii. 2517), and Cain and Nicoll ( J . C. S. 1902, 1412). In each 
case the rate of decomposition was measured by the rate of evolu- 
tion of nitrogen from the solution, but the liquid was not stirred 
or agitated in any way. Hantzsch conducted the reaction in a flask 
which was filled to the neck with the solution, exposing only a small 
surface of liquid to the gas above the solution, and thus furthering 
supersaturation. From time to time the flask was tapped to release 
any bubbles which had been formed at the bottom of the flask. 
Cain and Nicoll used a similar method in their investigations. 
Both workers found it was impossible to get results consistent 
with their theory of a unimolecular action throughout a greater 
range than about 30 to 80 per cent, of the total reaction. 
The diazo salt was prepared according to the method given by 
Cain and Nicoll from an ice-cold solution of aniline hydrochloride, 
to which was added a solution of sodium nitrite. In some cases it 
was found convenient to use solutions which gave off a greater 
volume of gas than the capacity of the burette. In such cases 
when the greatest amount of gas that could be measured had 
collected in the burette, the three-way tap at the top was turned 
so as to cut off the reaction vessel ; the levelling tube was then 
raised so as to bring the water again to the first division of the 
burette, the tap turned, and the measurement continued. 
In conducting the experiments the requisite amount of diazo- 
benzene chloride solution was taken and heated as rapidly as 
possible in a small flask over a Bunsen flame to a temperature 
one or two degrees higher than that of the water bath, so that 
after the slight cooling brought about by pouring through a funnel 
into the reaction vessel, the liquid should be as nearly as possible 
at the temperature of the bath. This occupied from '6 to T6 min., 
and the liquid was then immediately poured into the reaction 
vessel and the motor started. 
When the liquid had been violently churned for '5 min. in 
order to get rid of the gas with which the solution had become 
supersaturated, and to bring the solution to the temperature of 
the water bath, the three-way tap at the top of the burette was 
turned and the measurement of the rate of evolution of gas was 
commenced. Measurement was continued until the evolution of 
gas had become extremely slow, in many cases only 1 or 2 per cent, 
of the diazobenzene chloride being undecomposed when the last 
observation was taken. 
In the following tables are given observations taken during 
experiments performed at temperatures 36 o- 0, 44 0, 3, 51 0, 4, 60 o- 0, 
and 67 o, 0. 
