VARIATION OP MOLECULAR SURFACE-ENERGY WITH TEMPERATURE. 663 
pressed by a screw; it entered an iron cylinder C, carrying a screw plunger, not 
shown in the figure. The cylinder was filled with mercury, and by screwing the 
plunger in and out the pressure could be varied within wide limits, and the liquid in 
the tube could be exposed to any desired pressure, greater than that of the 
atmosphere. The temperature of the liquid could be controlled by means of the 
vapour-jacket, by the arrangement shown in the figure. The liquids in the bulb B 
boiled under known pressures, regulated by the gauge M, and the temperature could 
be varied at will. (For further details see ‘ Trans. Chem. Soc.,’ vol. 47, p. 640, and 
‘ Phil. Trans.,’ 1887, A, p. 69.) As in the experiments of Ramsay and Young, the 
liquids employed to secure constant temperatures were:—(1) Alcohol (40° to 70°), 
(2) chlorobenzene (70° to 130°), (3) bromobenzene (120° to 150°), (4) aniline (150°' 
to 180°), (5) quinoline (180° to 230°), (6) bromonapbtlialene (220° to 280°), and 
(7) dibenzylketone (280° to 330°). 
The method of filling the tube free from air, was as follows :—The tube 'v^as dis¬ 
connected, the cap N slipped along T towards the bend, and the projecting end of 
Fig. 3. 
the glass tube was sealed to a bulb, a constriction being left between the tube and 
the bulb, and also on the tube on which the bulb was blown, as shown in the figure. 
The liquid was then introduced into the bulb, some mercury was added, and the tube A 
was then connected with an air-pump, the liquid being heated, if necessary. After 
