C. M. Warren on the Volatile Hydrocarbons. 223 
to the custom of taking boiling-points with the bulb in the vapor, 
appear to be even greater than those which Kopp has raised 
the surface of the liquid; 
nd, that, with the bulb in the vapor, the thermometer is 
more liable to sudden depression from currents of cool air 
jug over the retort. If the bulb be in the vapor, the occurrence 
of either of these disturbing influences would then affect the 
Principal mass of the mercury in the thermometer; while, on 
the contrary, if the bulb were in the liquid, only the small quan- 
uty of mercury in the stem of the thermometer would be sub- 
Jected to these influences; the liquid then serving as a shi spa 
ge 
= 
small. I have n : 
of 3°-4° in distilling a body boiling as high as 98° C., without an 
‘Unne ‘i fl But the liquid in this instance was 
— unn rily 
_ pretty low in the retort. 
_ In the case of liquids boiling below the common temperature, 
it seems indispensable that the bulb of the thermometer should 
be placed in the liquid. As evidence of this I will here state 
the results of observations made while occupied in i 
troleum. 
. Some exceedingly volatile products from American pe 
Memoir “On Process of Fractional Condensation,” Memoirs of the At 
1864, and this Journal, last vol., p. 327. oth 
