ON EVAPORATION AND DISSOCIATION. 
75 
one. The experimental tube A was surrounded with a jacket B, and passed through 
an indiarubber cork, inserted into the lower opening of the jacket. In order to 
prevent this cork from being attacked by the hot condensed liquid, it was covered 
with a layer of mercury C. (It may be remarked here that it was found that the 
slight volatilization of this mercury did not affect the temperature, even at a tem¬ 
perature of 280°, with bromonaphthalene as a jacket, owing probably to the constant 
presence of a layer of liquid on its surface.) The pure liquid, the vapour of which 
served to heat the experimental tube, was boiled in a bidb, D, fused on to the side of 
Fig. 1. 
the jacket. A narrow tube was fused on to the top of the jacket, and was surrounded 
by a short condenser, E. On issuing from the condenser, the upper extremity of the 
narrow tube was coupled, by means of lead tubing, with a reservoir, F, the object of 
which was to collect any liquid which might accidentally pass the condenser. A 
second lead tube joined F with the gauge G, and the gauge was connected with a 
Carre’s air-pump, as well as with a Strengel pump, a large reservoir being interposed 
in order to ensure constancy of pressure. A barometer, H, stood in the same trough 
as the experimental tube A, and was surrounded by a jacket of water of known 
temperature, I. On account of the gradual escape of air from the glass into the 
vacuous space, the barometer was boiled out from time to time. Another barometer, 
l 2 
