ATMOSPHERIC PRESSURE BETWEEN 104 C. AND 115 C. 



437 



jacket IB d6/Q, where k l is some constant. If, on the other hand, there had been no 

 counter current, the heat-loss would have been due to radiation alone and would have 

 been represented by a term hdQ. With the counter current there will still be 

 radiation, and the term representing the total heat-loss will be of the form (h + kfQ) d6. 

 If we assume that the heat-loss h^ d9, by direct radiation from the upper part of the 

 flow-tube to the jacket, is of the same order as that fraction of the heat-loss h 2 d6 

 gained by the up-current from the lower part of the flow-tube, which is returned 

 into the flow-tube, and if this equivalence exists when the upper part of the flow-tube 

 includes a length extending to 6 cm. below the heating coil, the fi d6 term will 

 represent the total direct radiation loss from the lower part of the flow-tube to the 

 jacket, and the k/Q,d9 term, the heat lost from the upper part of the flow-tube to the 

 jacket. If this assumption is correct we should expect to find k constant in all the 

 experiments made with a definite calorimetric arrangement ; moreover, k should be 

 proportional to the value of the heat-loss per centimetre. Since the thermal exchanges 



050 



2-000 



001 



Fig. 11. 



D Silica calorimeter. 

 O Other calorimeters. 



which occur between the two currents of steam, and between these and the outer 

 brass jacket, are undoubtedly very complex, the above explanation must only be con- 

 sidered as approximately describing what is taking place. It has been put forward 

 mainly in order to justify, to some extent, the adoption of the type of equation used 

 in the calculations. The values of S c obtained show a distinct variation with the 

 magnitude of k, i.e., with the value of the heat-loss per degree per centimetre (fig. 11). 

 The extrapolated value of the specific heat, corresponding to zero heat-loss, is only 

 0'05 per cent, higher than the mean deduced from the results obtained under the 

 best experimental conditions, hence this value has been taken as the final result of 



these experiments, 



S = 2'0300 joules per gr. deg. at 104'5 C. 



S = 0'4856 calories per gr. deg. at 104 '5 C., 

 this latter result being in terms of the calorie at 20 C. 



