418 Mr. F. A. Waterman on an Improved Calorimeter 



and in adding water just sufficient in amount to maintain the 

 initial temperature of the cup. A little practice in the mani- 

 pulation of the calorimeter enables the operator to keep the 

 cup practically at its initial temperature throughout each 

 determination, thus obviating the use of radiation correction 

 and " water equivalent " of the cup. The falling of the cold 

 water from the water-dropper into the tube-shaped cup also 

 serves to agitate the water in the cup, and keeps its tempera- 

 ture uniform without the use of a stirrer. 



The cup and its contents are then removed from the bulb of 

 the air-thermometer and weighed. The weight thus obtained 

 minus the initial weight of the cup, water contained, and 

 weight of metal used, gives the weight of cold water added. 

 The loss in weight due to the evaporation of the water in the 

 cup, during the time required for the necessary observations, 

 is practically inappreciable, as the average loss was found to 

 be less than ^ milligramme. If desired, a correction based 

 upon preliminary observations may be introduced to compen- 

 sate for this loss. 



The necessary operations, briefly stated, are thus : — 



The heating and the determination of the temperature of a 



body of known weight. 

 Weighing of the cup containing a suitable amount of 



water. 

 Determination of the initial temperature of the cup. 

 Introduction of the heated body into the cup, quickly 

 followed by the introduction of an amount of cold 

 water sufficient to maintain the initial temperature of 

 the cup ; the temperature of the cold water being 

 observed during this operation. 

 Final weight of the cup and its contents determined, and 

 the weight of cold water added determined from data 

 obtained. 

 Calculation of result by use of the equation 



~_ ms(6 — t) 

 M(T-0)' 



The results obtained bv the use of this calorimeter, which 

 are here given, are but a summary of some trial determina- 

 tions made from time to time as the apparatus was being 

 improved*. As chemically pure metals were not at hand, 

 the results obtained are submitted simply for the illustration 



* I take this opportunity of expressing my thanks to Prof. W. F. 

 Magie and Mr. F. F. Thompson, t ellow in Experimental Science, for 

 kind assistance given me. 



