OF GASES AT CONSTANT VOLUME. 
945 
internal volume was 86'127 cub. centims. at 16°’7 C. Comparing these last witli 
the first results, obtained before the testing of the sphere, we find that the first 
results give a volume of copper of 15'584 ; the last results, 15’611. The results of 
the measurements of volume therefore agree satisfactorily, and, for the experiments 
of Tables I. to XII., the foregoing volumes are adopted. 
Upon the completion of the experiments of Table XII., a new series, involving 
much higher pressures, being entered upon, a preliminary test of the sphere was made 
with the first charge of CO 3 dealt with. This weighed 18’76 grammes. With this 
charge the sphere was heated for 15 minutes in steam. There was no leakage 
whatever, and a determination of the external volume revealed that this had risen to 
105‘595 cub. centims. If from this the volume of copper, 15'611, is taken, the 
internal volume is found to be 89’984, a further increase of 3‘85 cub. centims. This 
volume applies to the results given in Table XV., as well as to all those subsequently 
made, recorded in Part III. ; for a last determination of the external volume, at the 
completion of all the experiments, gave 105’520 cub. centims. at 1 1°‘5 C., showing 
that there was no further increase. These details are given here connectedly as 
drawing attention to the necessity of careful observation of the volume of the vessel 
when making such experiments. Otherwise serious error might be introduced into the 
calculation of the density of the gas. It would appear as if the change of volume was 
all along mainly due to change of shape. If drawing of the copper had been going on 
to any considerable extent, the prolonged and severe strains incident to the experi¬ 
ments of Part III. must have produced a marked increase of volume. No such was 
measured, however. 
The elastic yielding of the vessel was determined by an experiment in which 
10‘542 grams, of CO 3 at the temperature 16°'3 were released from the sphere, its 
external volume being accurately determined (by its displacement in water) before 
and after the release. A loss in buoyancy of 0'089 gramme of water at 16°'3 
occurred, which, reduced to cub. centims., gives the shrinkage as 0’0891 cub. centim. 
due to a decrease of pressure of 44'5 atmospheres. This shrinkage is so small that a 
mass of gas inserted in the sphere may be determined without correction by simply 
weighing the vessel before and after filling. Thus, in the above case, the neglected 
correction upon W for change of displacement in air at 16° and 760 millims. has the 
value 0*0891 X 0*00122 = 0*00010 gramme. As this is the case of a considerable 
charge of gas, such a correction is evidently negligible. 
It is, perhaps, further of interest in connection with the particulars of the vessel 
employed for holding the gas to observe that there is a precipitation of over 2 grammes 
of steam due to its own calorific capacity between an air temperatui-e of 10 ° and 
steam at 100 ° C. The experiments, however, show that some 4 or 5 grammes of COo 
(giving precipitations of about 0*135 and 0*172 gramme over a similar range) may be 
dealt with, and the specific heat determined readily to about 1 per cent, of accuracy 
(see Tables VII., VIII., XI., XII.). Experiments on a mass so small as 3 grammes 
MDCCCXCIV.—A. 6 E 
