186 MAX KLEIBER 



sites for leaders of research in these fields, because they have to de- 

 sign apparatus and develop methods for their particular problems. 

 Calorimetric frontier work such as myothermic and neurothermic 

 measurements in periods measured in milliseconds taxes to capacity 

 a well trained and critical mind of a physicist combined with the in- 

 genuity of a clever engineer. 



2. Adiabatic IVIeasurenients 



Adiabatic measurements are those in which there is no energy 

 exchange with the environment. Typical representatives of adia- 

 batic apparatus are the ice calorimeters. The heat produced or re- 

 leased in the instrument is measured by the amount of ice melted. 

 The result may be calculated as follows : 



AQ = 79.71M (8) 



where AQ is the heat developed (in calories) and M is the mass of ice 

 melted at 0°C. (in grams). 



Lavoisier and Laplace measured the amount of ice melted by 

 weighing the water that ran off from a pack of ice surrounding the 

 source of heat, such as a guinea pig. The ice pack was surrounded 

 by a jacket of water and ice. 



The amount of ice melted may be measured more accurately by a 

 decrease in volume. The relation between the decrease in volume 

 and the amount of ice melted may be stated as follows: 



M = AF/i 1000 ^ ) = 11.05 A7 (9) 



/ V 0.917/ 



where M symbolizes the amount of water melted in grams, AT' the 

 decrease in volume of the ice water mixture, 1.000 the density of 

 water at the freezing point, and 0.917 the density of ice at the freez- 

 ing point. Substituting this relation for M in equation (8) one finds 

 finally : 



AQ = 79.71 X 11.05AF = 880.8 AF (10) 



The use of the contraction in vohnne by melting of ice as a calo- 

 rimeter is credited to Hermann, a Russian scientist, who invented this 

 method in 1834. In 1870 Bunsen applied this principle for his well 

 known calorimeter, which is used mainly for measuring specific heat. 

 For a thorough discussion of the precautions necessary in the use of 



