406 
CHEMISTRY: RICHARDS AND COOMBS 
Great difficulty and considerable liability for error were found in the 
inequalities of the glass of the tubes to be measured. Accordingly all 
measurements were made in reversible apparatus of the type shown in 
the diagram. This form of apparatus vvrhen exactly half filled with 
liquid is observed, first in an upright position in front and behind, and 
again in an inverted position in front and behind. Thus from the av- 
erage, all the displacements due to refraction of irregular walls of the 
larger tube are entirely eliminated. The regularity of the walls of the 
smaller tube are tested by the calibration in the first place. 
The preliminary results thus obtained are recorded in the table given 
below. All the measurements were made in the presence of air. The 
surface-tensions are calculated according to the well known equation 
7 = i rhg (si - S2) in which the angle of contact of the meniscus in the 
tube is assumed to be zero. 
CAPILLARY CONSTANTS AND SURFACE TENSIONS 
Data obtained with Apparatus III (20.00°) 
Radius of capillary = 1.0099 mm. 
8UB8TANCK 
AVERAGE 
HEIGHT 
IN MM. 
CORRECTION 
FOR SM.^LL 
MENISCUS 
CORRE.CTED 
HEIGHT IN 
MM. 
DENSITY 
2074° 
CAPILLARY 
CONSTANT 
SURF AC a 
TENSION 
DTNES 
PER MM2 
Water 
Benzene 
Toluene 
14.394 
6.351 
6.369 
0.321 
0.311 
0.311 
14.715 
6.662 
6.680 
0.99823 
0.8788 
0.8658 
14.861 
6.728 
6.736 
72.62 
28.94 
28.58 
Data obtained with Apparatus IV (20.00°) 
Radius of capillary = 0.1936 mm. 
Benzene 
Methyl alcohol 
Ethyl alcohol 
Isobutyl alcohol .... 
Ethyl butyrate 
34.620 
30.063 
29.720 
30.016 
29.403 
0.061 
0.061 
0.061 
0.061 
0.061 
34.681 
30.124 
29.781 
30.077 
29.464 
0.8788 
0.7918 
0.7892 
0.8019 
0.8789 
6.714 
5.832 
5.766 
5.823 
5.704 
28.89 
22.61 
22.27 
22.86 
24.53 
It will be noted that, in general, these results are higher than most 
of the earlier results, for the reasons already suggested. For example, 
Quincke found only 14.47 as the capillary constant of water, and Renard 
and Guye found 6.47 for that of benzene. The carefully obtained re- 
sults of Walden and Swinne, although measured in a fairly satisfactory 
apparatus, are all subject to the same error, because the apparatus was 
calibrated by means of a value of the capillary constant of benzene 
which is too low. It is hoped that an exact evaluation of the amount 
of this error may make it possible to correct the comprehensive and valu- 
