42 Mr. P. J. Hartog and Dr. J. A. Harker on 



apparatus described, for if we have the gas burner above 

 the calorimeter alight, as it is during a determination, 

 there is no means of preventing the liquid from condensing 

 in the calorimeter. Thus the Berthelot correction cannot 

 be applied. 



The other method of correction in use is that of 

 Regnault and Pfaundler. It assumes that the change in 

 the temperature-rise (or fall, as the case may be) per 

 minute is proportional to the change of temperature. 



Suppose during the preliminary period that we observe 

 the thermometer for n minutes, during which time it rises 

 through the small interval t q — 1 . Then we may assume 

 that at the mean temperature 



the rise per minute would be 



This last quantity we call the initial correction. 



Again in the final period the thermometer rises during m 

 minutes through the small interval t g — t r . Then similarly 

 we call the final correction the quantity 



t s -t r 

 m 



corresponding to the mean temperature 



t r + t s 



We then plot out temperatures as abscissae, and the 

 corrections corresponding to those temperatures as ordinates. 



