Art. XL — On alMethod of Determining the Specific Heat 

 of a Liqiiid, especially of Solutions. 



(With Diagram). 



By Walter Rosenhain. 



[Eead 12th AiTgiist, 1897.] 



The subject^of the j^resent research was suggested to me in 

 November, 1896, by Professors Lyle and Masson, and my object, 

 in the tirst place, was to tind a convenient and satisfactoiy method 

 for the accurate determination of the .specific heats of liquids ; 

 this method it was intended to apply to an extensive series of 

 determinations of the specific heats of solutions, with a view to 

 establishing on an accurate basis the relation between the degree 

 of concentration and the specific heat of a solution. AVith this 

 object in view, the experimental method was required to comply 

 with a variety of somewliat contradictory conditions. Accuracy 

 being the primary object, the most desirable course seemed to be 

 to follow tlie lead of Griffith and other recent workers in calori- 

 metry, and make the experiments on a large scale, and to use 

 large masses of the substances to be experimented upon ; but, on 

 the other hand, some of the substances to be used were likely to 

 be rare chemicals, and the great expense prohibited the use of 

 large quantities. Further, as such substances as alcohol, ether, 

 chloroform etc., were to be used as solvents, the prevention of 

 evaporation became of importance. Beyond these special con- 

 ditions applying to the particular pui'pose in view, the general 

 considerations afTecting all calorimetric methods, such as the 

 accurate measurement of the various temperatures involved, pre- 

 vention or measurement of the loss of heat by radiation, and the 

 efficient stirring of the contents of the calorimeter had all to be 

 carefully regarded. 



The first method which was tried depended upon the thermo- 

 electric measurement of a difierence of temperature. 



The calorimeter was a cylindrical vessel of thin brass, nickel- 

 plated ; it hung by a flange packed up with asbestos-paper, inside 

 another similar but larger vessel forming an annular air-space ; 



2a 



