14 PROPERTIES OF STEAM AND AMMONIA 



reduce from the 2O-degree calorie to the mean calorie, the equation for 

 i' becomes 



t ' - 0.9838 / + 2.0856 log (/ -f 4) 4- 0.233 



For temperatures above 212 degrees, two sets of experiments are 

 available, Regnault's and Dieterici's, neither of which can be accepted 

 as thoroughly reliable. Regnault's results have been recomputed by 



400 

 Temp. F. 



FIG. 6. HEAT CONTENT OF WATER, 2i2-6oo F. 



various investigators. In Fig. 6, six mean values deduced from Cal- 

 lendar's computation are shown. The ordinates in this figure represent 

 values of 



A*'. ,"-(/- 32), 



that is, the excess of the heat content over / 32, the temperature range. 

 Abscissas are temperatures F. In the same figure are shown the points 

 obtained by Dieterici. The curve D represents the equation adopted by 

 Dieterici and curve C represents Calendar's equation extended beyond 

 212 degrees. 



Callendar questions the accuracy of Dieterici's experiments and gives 

 preference to his equation extrapolated through the range ioo-2OO C. 

 It is probable that Dieterici's points are considerably in error, as the 

 method of the experiments involved large corrections, and it is also 

 probable that Regnault's points are no more reliable. However, there 



