68 



HEAT. 



whence w = 1 3'5 nearly, 



or we may regard the calorimeter, thermometer, and stirrer as 13'5 

 grammes of water extra. 



To find the specific heat of the brass, again let us start with the 

 calorimeter containing 100 grammes of \\ater at 15. The brass, 

 which we may suppose weighs 150 grammes, has been for some time 

 in the steam-jacketed chamber or heated vessel. For simplicity, let us 

 take its temperature as exactly 100. It is quickly dropped into the 

 water, and the calorimeter is stirred. Let the temperature readings be 



maximum, \ minute after mixture .. . 23'8 



1 minute after maximum .... 23*6 



2 minutes ,, ,, .... 23'4 

 Final rate of loss of heat corresponds to fall of 0'2 per minute. 



,, ,, ,, O'l per \ minute. 



Loss during rise . . . . . . 0'05 



The corrected maximum is therefore 23-85. 



If sf is the specific heat of brass on the average of the range from 100 

 to 23-85, then 



Heat lost by brass = Heat gained by calorimeter 

 gives 150*(100 - 23-85) = (100 + 13-5)(23-85 - 15), 



whence s = 0-0879. 



Regnault's Determinations by the Method of Mixtures. 



Experiments on Solids. Regnault used the method of mixtures for the 



D 



A A 



FIG. 53. Regnault's Apparatus for Determination of Specific Heat 

 of Solids by Method of Mixtures. 



determination of the specific heats of a large number of solids, liquids, 

 and gases. When working with solids he used an apparatus, the 

 principle of which is shown by Fig. 53. 



