PEOFESSOB KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 
99 
determination of which is important, dissolve in. water, and hence I had to use a different 
liquid. Coal-tar naphtha has. the advantage that it is a mobile liquid, does not dissolve 
most salts, and does not resinify in contact with the air ; but besides the disagreeable 
odour, with continuous working, respiring air charged with its vapour appears to act 
injuriously on the organs of the voice. As compared with water, coal-tar naphtha has 
the disadvantage, that its specific heat must be specially determined, and any possible 
uncertainty in this is transferred to the determination of the specific heat of the solid 
substance ; but the thermal action of a given volume of naphtha is only about ^ that of 
the same volume of water*; and in experiments in which the thermal action of a solid 
substance is determined, along with that of the necessary quantity of liquid which is 
contained with that substance in a glass, the thermal action due to the solid is a larger 
fraction of the total if coal-tar naphtha is used than if water is the liquid, which is a 
favourable circumstance in the accurate determination of specific heat. As it was more 
especially important for me to obtain comparability in the results for specific heat, I 
have, for a great many substances which are insoluble in water, and for whose investi- 
gation water might have been used, also employed coal-tar naphtha. Water was used 
for a few substances which are soluble in coal-tar naphtha (sulphur, phosphorus, ses- 
quichloride of carbon, for instance). Several substances I determined both with water 
and with naphtha ; the results thus obtained agree satisfactorily. To the question as to 
whether any possible change in the specific heat of naphtha with the temperature can 
be urged against the use of this liquid, I shall return in § 29. 
27. The coal-tar naphtha A which I principally used in the subsequent experiments 
was prepared from the commercial mixture of hydrocarbons G n H 2 „_ 6 , by purifying it by 
means of sulphuric acid, treating the portion which distilled between 105° and 120° 
with chloride of calcium for six days, then again rectifying it, and collecting separately 
that which passed between 105° and 120°. This liquid had the specific gravity 0-869 
at 15°; in determining its specific heat I made four series of experiments, two at first 
when I was engaged on experiments in which I used this naphtha, and two towards 
the end. 
I. — Experiments with Glass 1. Temperature of the Air 12°T-12°-9. 
T. 
T'. 
f. 
t. 
M. 
/• 
X . 
sp. H. 
O 
o 
0 
o 
grms. 
grms. 
grm. 
46-1 
13-8 
13-51 
11-24 
26-99 
2-875 
0-651 
0-433 
48-6 
14-0 
13-71 
11-24 
26-945 
2-875 f 
55 
0-443 
45-5 
14-1 
13-83 
11-59 
26-97 
2-975$ 
55 
0-439 
45-3 
14-3 
14-01 
11-80 
26-94 
2-970 f 
55 
0-428 
Mean . . . 0-436 
* The specific heat of the coal-tar naphtha A, with which I made most of my experiments, is 0 - 431, and its 
specific gravity at 15°=0869. 
f After drying the stopper. 
After adding some; naphtha. 
