PHYSICAL CHAEACTEES OE MIXTURES OE ALCOHOL AND WATEE. 607 
The height of the thread of liquid in the capillary tube is now to be read off by 
means of the scale etched on the glass rod. To do this with sufficient accuracy, a 
telescope, capable of horizontal and vertical movement, and furnished with cross wires 
in the eyepiece, is used. 
A small U-tube, containing spirit, is fixed near the capil- 
lary tube ; the eyepiece of the telescope is turned round till 
one of the cross wires just touches the two menisci in the 
U-tube ; thus the cross wire is placed accurately horizontal. 
On slightly turning the telescope horizontally, and, if neces- 
sary, raising it vertically, the horizontal wire can be made 
to touch the meniscus in the capillary tube, and at the same 
time cut the divisions etched on the glass rod; the point 
where the wire thus crosses the millimetre-scale is read off, 
and thus the height of the thread above the surface of the liquid is determined. 
This method gives very accurate results, if care be taken in the various adjustments. 
The following Table gives the results obtained. 
Column 1 gives the percentage of alcohol by weight. 
Column 2 gives the observed height of the thread, in millims. 
Column 3 gives the height supposing water stood at 100 millims. 
Column 4 gives the length of a column of water equal in weight to the thread of 
alcoholic mixture in column 3, and affords, therefore, a measure of the relative strength 
of the molecular attraction in the various mixtures. 
Column 5 gives the heights calculated on the assumption that they will be propor- 
tional to the weight of the constituents of each mixture. 
Column 6 gives the difference between Columns 4 and 5. 
Table X. 
A thread of mercury in the capillary tube, 121-5 millims. long, weighed 04426 grin., 
giving 0584 millim. as the diameter of the tube. 
The temperature at which the experiments were made was 16° C. 
1. 
Alcohol 
per cent. 
2. 
Height 
observed. 
3. 
Height, assuming 
water =100 millims. 
4. 
Relative molecular 
attraction. 
5. 
Height 
calculated. 
6. 
Difference. 
0 
49-47 
100 
100 
100 
10 
34-22 
69-17 
68-07 
93-11 
-25-04 
20 
27-92 
56-43 
54-83 
86-22 
31-39 
30 
23-84 
48-19 
46-15 
79-34 
33-19 
40 
22-41 
45-30 
42-56 
72-45 
29-89 
45 
21-64 
43-74 
40-64 
69-00 
28-36 
50 
21-24 
42-93 
39-43 
65-56 
26-13 
60 
20-93 
42-30 
37-89 
58-68 
20-79 
70 
20-66 
41-76 
36-42 
51-79 
15-37 
80 
20-43 
41-29 
35-03 
44-90 
9-87 
90 
20-06 
40-54 
33-35 
38-02 
4-67 
100 
19-40 
39-21 
31-13 
31-13 
Fig. 3. 
4 m 2 
