PHYSICAL CHAKACTERS OE MIXTURES OE ALCOHOL AND WATER. 613 
as they both reach a maximum deviation from the calculated mean at 45 per cent. These 
two properties have been shown to be connected with each other by Deville and Hoek, 
Ann. de Chim. et de Phys. 3rd series, v., and Pogg. Ann. cxii. 
Properties which are more nearly chemical than physical, as the solubility of various 
salts, have also been examined ; some of these salts, as potassic chloride, reach a maxi- 
mum deviation from the mean solubility at 30 per cent, alcohol ; others seem to reach 
the maximum deviation at 40 per cent, and 45 per cent. ; but the subject requires further 
investigation. 
Thus the whole of the physical characters of mixtures of alcohol and water come to 
a maximum deviation from their theoretical values somewhere between 30 per cent, 
and 45 per cent, alcohol by weight ; the 30 per cent, alcohol nearly corresponds to the 
formula C 2 H 6 0 + 60 H 2 , which actually gives 29 - 87 per cent.; whilst 45 per cent, is 
nearly represented by the formula C 2 H 6 0 + 30 H 2 , which really gives 46 per cent. 
Some of the physical characters examined seem to be especially connected with each 
other; these are: — 
1. Specific heat and heat produced by mixing; for by dividing the number of units 
of heat evolved by 5 grms. of any mixture by 3’411, the elevation of the specific 
heat of such mixture above the theoretical specific heat is obtained. 
2. Boiling-point and capillary attraction, which in a similar way can be calculated 
from each other. 
Deville and Hoek have shown the specific gravity and index of refraction to be con- 
nected with each other. 
Whether these relations hold good with other similar substances, whether in fact 
these experiments have brought forward one example of a general law, or only disco- 
vered a singular anomaly, must be left for further research to decide. 
Explanation of the Plate. 
PLATE LXIV. 
UPPER HALF. 
Curve 1 gives the specific heats ; the vertical lines represent the percentage by weight of 
alcohol in this and all the following curves. 
The horizontal line gives the specific heat, water =100. 
Curve 2. The horizontal lines give the boiling-points in degrees Centigrade. 
Curve 3. The horizontal lines give the capillarity in millims., water=100 millims. 
Curve 4 . The horizontal lines give the expansion for 10,000 volumes. 
Curve 5. The horizontal lines give the compressibility in millionths. 
LOWER HALF. 
The vertical lines, as in the upper half of the Plate, give the percentage of alcohol. 
mdccclxix. 4 N 
