606 DR. A. DUPRE AND F. J. M. PAGE ON THE SPECIFIC HEAT AND OTHER 
caution is not taken, the condensed liquid is apt to block up the tube and prevent the 
free escape of the vapour ; should this occur, the pressure in the flask is slightly increased, 
and a corresponding rise in the boiling-point at once takes place. 
The thermometer employed had a range from 65° to 100° C., divided into tenths of a 
degree ; and thus T ^o of a degree could be read off. 
The following Table gives the result of the experiments, the barometer standing at 
744-4 millims. 
The third column gives the boiling-points calculated on the assumption that the two 
bodies, alcohol and water, influence the boiling-points of the several mixtures in pro- 
portion to the weights of each which those mixtures respectively contain. 
Table IX. 
Per cent, by weight 
of absolute alcohol. 
Boiling-point 
observed. 
Boiling-point 
calculated. 
Difference. 
0 
99-4 
10 
90-98 
97-25 
-6-27 
20 
86-50 
95-10 
-8-60 
30 
84-01 
92-95 
— 8-94 
40 
82-52 
90-90 
-8-38 
45 
81-99 
89-72 
-7-73 
50 
81-33 
88-60 
-7-27 
60 
80-47 
86-50 
-6-03 
70 
79-61 
84-35 
— 4-74 
80 
78-84 
82-20 
-3-36 
90 
78-01 
80-05 
— 2-04 
100 
77-89 
Section IY . — Capillary Attraction. 
A capillary tube of convenient size and length is chosen, carefully cleaned with sul- 
phuric acid, alcohol, and water, and then thoroughly rinsed out with the mixture under 
examination. 
The capillary tube, thus prepared, is fixed vertically in an ordinary universal screw-clamp. 
A glass rod is taken, about the same length as the capillary tube ; its lower extremity 
is drawn out and bent aside, so that it terminates in a point at some distance from the 
axis of the rod. A millimetre-scale is etched on the glass rod, and the vertical distance 
of the point from the lowest division of the millimetre-scale is carefully measured. 
This glass rod is fixed to the capillary tube by two india-rubber bands, the point of 
the glass rod being some little distance above the lower extremity of the capillary tube. 
The liquid whose capillarity is to be estimated is placed in a small capsule, under- 
neath the capillary tube. The capsule is supported on a stand, whose height can be 
delicately adjusted by means of three screws. 
The stand is raised at first rapidly, then slowly, until the point of the glass rod just 
touches the surface of the liquid in the capsule. The moment when this contact 
between the point and the surface takes place can be observed with the greatest accu- 
racy ; and as the point is bent aside, it touches the surface beyond the influence of the 
capillary action of the external portion of the tube. 
