PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 
101 
relatively considerable space above the liquid remains empty, gives the specific heat of 
readily vaporizable liquids somewhat too high, but that at the same time this influence 
of the formation and condensation of vapour is very small in the conditions under which 
I worked*. — The number 0-431 obtained in the previous determinations expresses the 
thermal action due to the cooling of 1 grm. naphtha A through 1° in my experiments, 
which thermal action depends to by much the greatest extent on the specific heat of this 
liquid, and only to a very small extent on the condensation of the previously formed vapour. 
In calculating the experiments communicated in the third section, that number is taken 
as the expression for the thermal action of naphtha, which is put as proportional to the 
weight of the latter. This is, strictly speaking, not accurate, in so far as the thermal 
action arising from condensation of vapour only depends on the magnitude of the empty 
space and the temperature, and not on the quantity of naphtha in the glass. But the 
small possible inaccuracy due to this cause in my experiments is not to be compared 
with other uncertainties. The manner in which I have taken into account the naphtha 
contained in the glass corresponds most accurately to the actual conditions of the expe- 
riment, when this thermal action is most considerable (only naphtha in the glass ) ; and 
if my mode of calculation less satisfies these conditions (less naphtha in the glass), the 
entire amount is less considerable, and the influence of that which might be missed in 
that calculation, a vanishing quantity. 
29. My experiments have been made at very different temperatures. The tempe- 
rature of the air was often something under 10°, sometimes above 20°. These numbers 
represent the limits to which the liquid in the glass, together with the solid substance 
cooled in the calorimeter. In most experiments I heated the glass with its contents to 
about 50°, in some cases not so high. Now, for the various intervals of temperature 
within which the liquid in the glass cooled, can its specific heat be assumed to be 
always the samel For water this may be done, and for coal-tar naphtha I did not 
calorimeter (comp. fig. 6), was = 0-688 grm. A series of experiments in which this glass was used to 
determine the specific heat of the naphtha A gave the following results : — 
Temperature 
of the Air 15°-5- 
-15°-6. 
T. 
T'. 
t'. 
t. 
M. 
f. 
X. 
sp. H. 
O 
Q 
O 
grms. 
grms. 
grm. 
52-5 
17-8 
17-53 
14-93 
26-945 
3-205 
0-688 
0-415 
49-6 
17-4 
17-13 
14-73 
26-955 
„ 
„ 
0-412 
50-9 
17-6 
17-29 
14-83 
26-96 
„ 
„ 
0-407 
50-5 
17-6 
17-26 
14-83 
26-975 
„ 
„ 
0-407 
51-6 
17-7 
17-38 
14-84 
26-985 
„ 
„ 
0-416 
50-9 
17-8 
17-47 
15-03 
26-94 
„ 
„ 
0-405 
Mean . . . 0-410 
* This is seen from the experiments on water communicated in § 25, and from the subsequent determinations 
in the next section, in which water was contained in the glass along with the solid substance. 
