24 
MR. J. W. CAPSTICK ON THE RATIO OF THE SPECIFIC HEATS 
dry ether and dropped into distilled water. The gas came off without undue violence, 
and the deposit of zinc oxide left in the flask was pure white. 
The gas was collected over a large quantity of boiled water, and shaken with it to 
remove as much of the ether as possible, and in the first two experiments it was 
passed slowly into the Kundt apparatus through two sets of Geissler bulbs containing 
sulphuric acid. 
On opening the apparatus the ethane was found to be without smell, but to ensure 
the removal of ethyl iodide which, from its high density, would have a very prejudicial 
effect, in the other experiments, the gas was passed through one set of bulbs of 
Nordhausen acid, two of potash, and two of strong sulphuric acid. 
As it seemed undesirable, however, to introduce ether vapour, an attempt was 
made to prepare the ethane by dropping the zinc-ethyl itself on ice without diluting 
with ether. 
The result showed that the ether was necessary, for after repeated attempts, the 
residue left in the flask instead of being white, was always dark grey, and effervesced 
slightly with acid, showing the presence of metallic zinc. 
Moreover, analysis showed that there were heavy hydrocarbons present, for 
100 volumes of the gas gave, on explosion with oxygen, 227 volumes of carbon 
dioxide. After passing the ethane slowly through Nordhausen acid, 100 volumes 
gave 207 volumes of COg, so that the impurities are mainly unsaturated hydrocarbons, 
but probably there is some butane present. 
The cause of the impurity of the gas appears to be the violence of the reaction. 
The zinc-ethyl never got clear of the dropping tube, but was immediately acted on by 
the water vapour, and formed a great sjDongy clot round the end. This absorbed 
more zinc-ethyl, which was decomposed in its pores, and so the temperature rapidly 
rose high enough to bring about dissociation. It is known that at a moderately high 
temperature zinc-methyl decomposes into zinc and hydrocarbons, and probably a 
similar thing happened here. 
Table II. shows the results of the experiments, taking for the specific gravity of 
the gas the theoretical density, 1’0367. In all the experiments the pressure was 
that of the air. 
Table XI. 
t. 
/. 
V. 
Percentnge of air. 
7- 
9-8 
43-40 
48-10 
1-8 
1-185 
12 
43-48 
48-29 
0 
1-183 
14-4 
43-61 
48-52 
not determined 
1-180 
16-6 
43-82 
48-66 
not determined 
1-184 
16T 
43-80 
48-65 
2-9 
1-179 
Mean . . . 
1-182 
i 
