194 



MAX KLEIBER 



which may be of the Beckmann type, or may be an absolute thermometer 

 graduated to 0.01 °C. in order to permit the estimation of thousandths of a 

 degree. After a steady thermal state is reached during a preliminary period, 

 a small electric current is passed through the ignition wire, heating it so that 

 it burns and ignites the sample. 



Temperature leaks during the experiment may be estimated from tem- 

 perature readings at regular intervals in a preliminary period and a period of 

 steady change after the combustion. As a rule, five minutes will be suf- 

 ficient time for each of the three periods: preliminary period prior to ig- 

 nition, main period just after ignition, and after period, following the main 

 period. 



Fig. 5. Bomb calorimeter in cross section. 



A correction for temperature loss may be calculated on the basis 

 of Newton's law of cooling, which indicates the following relation: 



V = K{T - T,) 



(10) 



where V = rate of temperature loss in degrees Centigrade per minute 

 and K is the cooling coefficient or cooling rate per degree difference. 

 The difference T — T",. is known as "thermal head," where T is the 

 temperature of the calorimeter water and T^ is the temperature of the 

 environment (jacket). 



Application of this law leads to the following correction equation : 



