chemical change by measurement of the gases evolved. 595 
with the evolution of carbon monoxide (Dewar and Jones, 
J. G. S., 1904, 207). Experiments were first performed with 
chloroform as the solvent, but later absolute alcohol was sub- 
stituted because this solvent has the advantage of dissolving 
the nickel iodide formed during the reaction. Considerable 
difficulty was experienced in preventing the decomposition of 
the nickel carbonyl solution. The solution was eventually stored 
in a reservoir connected with a burette as illustrated in Fig. 5. 
The inverted flask A which serves as the reservoir is connected 
by means of the tube containing the stop-cock C to the lower part 
of the burette, whilst the upper end of the burette is sealed to 
a tube which also passes through the rubber stopper of the flask 
A till it almost touches the end. To this tube is sealed a branch 
tube containing the stop-cock B which is connected to a reservoir 
of carbon monoxide, wash bottles containing sulphuric acid, 
potash and pyrogallol being interposed to purify and dry the gas. 
The solution of nickel carbonyl in the burette and in the flask 
39 
VOL. XIV. PT. VI. 
