464 PROFESSOR W. RAMSAY AND DR. S. YOUNG ON THE INFLUENCE OF 
that the maximum temperature to which a solid, having free surface for evaporation, 
can attain is that at which its vapour pressure is equal to the gaseous pressure to 
which it is exposed during distillation. The apparatus was modified as described in 
§ 1 7 of that memoir. In reading pressures, parallax was avoided by the use of a 
mirror graduated in millimeters, standing vertically behind both gauge and barometer, 
and it was possible to read with confidence to the tenth part of a millimeter. (In 
testing this scale with a standard cathetometer by Mr. Darwin, of Cambridge, the 
greatest deviation observed was 0 - 026 millim. in a range of 200 millims.) Only two 
readings were required, and these involved no correction at low pressures. 
The cotton-wool having been moistened with benzene, the following readings were 
taken :— 
9. Vapour pressures of benzene. 
Temperature (corrected). 
Pressure (observed). 
Pressure (corrected). 
State. 
millims. 
millims. 
9-60 
44'5 5 
44-40 
Liquid 
8-20 
41'05 
40-90 
632 
37-20 
3710 
4-50 
33-30 
33-20 
4*46 
34-15 
34-05 
4-08 
33-45 
33-35 
4-01 
32-50 
32-40 
3'60 
32-65 
32 - 55 
3-00 
31-50 
31-40 
Solid 
2-98 
32-00 
31-90 
Liquid 
2-60 
30-00 
29-90 
Solid 
1-20 
27-40 
27-30 
0-90 
26-80 
26-70 
-0-20 
25-60 
25-50 
-1-28 
23-40 
23-40 
-1-72 
22-35 
22-35 
-2-80 
20-80 
20-80 
-3-77 
19-60 
19-60 
-4-80 
17-90 
17-90 
-5-21 
17-60 
17-60 
55 
10. The boiling point of this specimen of benzene, which had been purified by 
recrystallization fifteen times and then carefully dried and fractionated, was 80" at a 
pressure of 755'7 millims.; it melted at 3°'3. From Professor V. Meyer’s recent 
researches, however, it is probable that it still contained thiophene. The results are 
graphically shown in the accompanying curve, and it is evident on first inspection that 
the solid-gas curve is not continuous with the liquid-gas curve. We were unsuccessful 
in our attempts to cool benzene appreciably below its freezing-point without its 
solidifying. 
11. As acetic acid promised favourable results in this respect we subjected it to 
experiment. 
The results are given in the following table :— 
For series IV., V., VI., VII., and VIII., a thermometer graduated in tenths ot 
