2 
164 RESEARCHES ON THE VOLATILE HYDROCARBONS. 
flask were perfectly dry. It was these observations which first directed my attention 
to the fact that the temperature of the vapor could not in all cases be depended upon 
for the true boiling-point of a liquid, and naturally led me to make other experiments 
with special reference to this question. 
Experiment 2.— The conditions of this experiment were somewhat different from 
those of the first. The liquid operated upon was the extremely volatile product col- 
lected in the “second receiver” of Experiment 1. The flask employed was smaller, 
and provided with two thermometers; the bulb of one of these was placed in the 
liquid, and that of the other in the vapor. The flask stood in a water-bath containing 
ice-water ; this bath was also provided with a thermometer. The temperature of the 
ice-water bath was very gradually raised by means of a small flame from a Bunsen’s 
burner. Temperature of the laboratory, 20°C. Observations during the distilla- 
tion : — 
ponte of the water-bath, : ‘ : 10° 
1. “ boiling liquid, ‘ ‘ «8? 
“vapor, é ‘ ‘ 18°.5 
eee of the water-bath, . . fs «2? 
2. “ poiling liquid, . : : 9° 
“vapor, . i . 2 « 18° 
i of the water-bath, ‘ F . 18° 
15 minutes later. 3. “ boiling liquid, j . . 10° 
“  yapor, : F ‘ 14° 
ene of the water-bath, . ‘ é - 20° 
10 minutes later. 4. “boiling liquid, . a F 12° 
“ vapor, . ‘ ‘ ‘ eae 
Temperature of the water-bath,  . ‘ 23° 
20 minutes later. 5. i “  poiling liquid, - - 4 Ad? 
& “ vapor, . ‘ 4 . 19° 
Experiment 3.— The subject of this experiment was a liquid which I had separated 
from the most volatile product of the re-distillation, on a manufacturing scale, of the 
crude benzole obtained in the distillation of coal-tar. The apparatus employed was 
essentially the same as that used in Experiment 1, with the addition of the extra 
thermometers, as in Experiment 2. The condensing-worm in the “elevated bath,” 
and that in the “cold bath,” and also the “ first receiver,’ were all cooled in pounded 
ice. The condenser in the “refrigerator,” and also the “second receiver,’ were both 
