340 



Dr. A. Dupre on the Specific Heat fyc. 



[May 16, 



vessel holding liquid carbonic acid was employed, by means of which any 

 required pressure could be obtained with great facility. 



Table VII. 



Percentage 

 of methylic 

 alcohol, by 

 weight. 



Temperature 

 in degrees 



Compressibility for 

 1 atmosphere. 



Difference. 



Centigrade. 



Found. 



Calculated. 





o 



16 - 8 



0-00004741 







10 



165 



•00004368 



0-00005497 



-0-00001129 



20 



160 



•00004365 



•00006303 



•00001938 



30 



154 



•00004289 



•00007052 



•00002763 



40 



17-4 



•00004781 



•00007758 



•00002977 



50 



165 



•00004916 



•00008420 



•00003504 



60 



16-4 



•00005541 



•00009029 



•00003488 



70 



15-7 



•00006167 



•00009586 



•00003419 



80 



16-3 



•00007416 



•00010083 



•00002667 



90 



15-2 



•00009103 



•00010511 



•00001408 



100 



15-0 



•00010879 







All relations pointed out in the former paper as existing between^ the 

 various properties of mixtures of ethylic alcohol and water find their 

 parallel in the mixtures now under consideration. Certain sets of pro- 

 perties come to a maximum deviation from the calculated mean at the 

 same strength ; in some cases the values found are always below, in others 

 always above the calculated mean ; and in both mixtures the rate of expan- 

 sion shows the same singular peculiarity, viz. of being for certain mixtures 

 below, for others above the mean. In this, as in the previous mixture, the 

 specific heat and the heat evolved during mixture not only come to a 

 maximum deviation from the mean in mixtures of the same strength, but 

 all mixtures evolving the same amount of heat during their formation 

 possess a specific heat elevated to the same amount above the mean ; and, 

 moreover, the numerical relation between these two values is the same for 

 mixtures of every degree of strength. Hence, if the heat evolved in the 

 formation of 5 grms. of any of the mixtures be divided by 7'9, the eleva- 

 tion of the specific heat of this particular mixture above its calculated 

 mean value is obtained. Between the boiling-point and the capillary 

 attraction a somewhat similar relation is found. If in this case the ob- 

 served depression of the capillarity of any mixture below its calculated 

 mean value be divided by 1*9 (the capillarity of pure water taken as 100), 

 the depression of the boiling-point of this mixture below the mean is 

 obtained. 



It has been pointed out above that an intimate relation exists between 

 the heat evolved during the formation of a mixture and its specific heat. 

 A closer study of this relation has led the author to the following con- 

 clusions, which seem not only to hold good for the two mixtures now 

 under consideration, but to be of very general application ; they may be 

 formulated as follows. 



