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Dr. A. Dupre on the Specific Heat fyc, [May 16, 



May 16, 1872. 

 FRANCIS GALTON, M.A., Vice-President, in the Chair. 



The following communications were read : — 



I. " On the Specific Heat and other physical characters of Mixtures 

 of Methylic Alcohol and Water, and on certain relations existing 

 between the Specific Heat of a Mixture or Solution and the 

 Heat evolved or absorbed in its formation." By A. Dupre, 

 Ph.D., Lecturer on Chemistry at the Westminster Hospital. 

 Communicated by W. Odling, M.B. Received April 4, 1872. 



(Abstract.) 



The pure methylic alcohol used in these experiments was prepared from 

 rectified wood-spirit according to a process of E. Th. Chapman, being a 

 modified chloride-of-calcium process as originally recommended by Sir 

 Robert Kane. The anhydrous alcohol obtained had a specific gravity of 

 •81371 at 10° C. ; it boiled at a temperature of 58°*6 C. under a pressure 

 of 757*4 millims., had a specific heat of 58*325 between the temperatures 

 60° and 18°, and was perfectly miscible with water in every proportion. 

 When oxidized with excess of bichromate and sulphuric acid, it yielded 

 nothing but carbonic acid and water. 



Section 1. Specific Heat. 



This is estimated in the usual manner, by heating a known weight of 

 the liquid enclosed in a suitable vessel to a certain temperature, and 

 plunging it, vessel and all, into the water of a calorimeter ; the rise in tem- 

 perature produced will, with the necessary corrections, furnish the data 

 required for the calculation of the specific heat sought. This calculation 

 was performed by help of the following formula: — 



c- w 



m (T— t') m 



wherein C is the specific heat required ; 



W the water-value of the calorimeter and contents ; 

 t the temperature of the calorimeter at the beginning ; 

 t' the temperature of the calorimeter at the end ; 



t" the temperature of the calorimeter at the end plus the necessary cor- 

 rections ; 



T the temperature of the steam-oven ; 

 m weight of fluid or mixture employed ; 

 H water-value of vessel holding the mixture. 



The vessel to contain the mixture is an annular brass vessel, with a fan- 



