336 Messrs. Dupre and Page on the Physical Properties [Mar. 11, 



Weight of water contained in the piezometer 1 14*9727 grms. 



In conclusion the authors confine themselves to pointing out certain 

 relations which connect the various physical properties examined. 



These properties may he divided into two classes, according as they 

 reach a maximum deviation from the theoretical mean at 30 per cent, or 

 40 per cent. ; each of these is divided into two subclasses, one containing 

 those properties in which the numbers found are above those calculated, 

 and the other containing those in which they are below. 



Class I. 



Subclass a. Specific heat. 



Heat produced by mixing. 

 ,, b. Boiling-point. 



Capillary attraction. 



Class II. 



Subclass c. Rate of expansion. 

 ,, d. Compressibility. 



Other characters, examined by previous investigators, are : — 



1. Vapour-tension : this falls under Class I. Subclass b. 



2. Specific Gravity. 



3. Index of Refraction. 



The two latter form a new class, coming to a maximum deviation from 

 their theoretical value at 45 per cent. 



In subclass a, specific heat — by reference to the Tables given, it will be 

 seen that the first addition of alcohol to water (though alcohol has a 

 specific heat much lower than that of water) produces mixtures which 

 have a higher specific heat than water, and that a mixture contain- 

 ing between 30 and 40 per cent, alcohol has the same specific heat as 

 water. 



Similarly alcohol, though much more compressible than water, yet, 

 when added to it, forms mixtures less compressible than water; so that a 

 mixture containing between 45 and 50 per cent, alcohol has the same 

 compressibility as water. 



The rate of expansion is remarkable, as, starting from water, it at first is 

 below the theoretical value, then rises; at 17 to 18 per cent, the rate of 

 expansion is identical with the calculated expansion ; for all mixtures 

 stronger than this, the rate of expansion is constantly above that calcu- 

 lated. 



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, 

 nearly corresponds to the formula C 2 H 6 + 6 OH 2 (=29*87 per cent.) ; 



