2 PROPERTIES OF STEAM AND AMMONIA 



Development of a General Theory. --The various thermal properties 

 of a vapor an rrl.itnl through well -known thermodynamic laws. Thus 

 the Clausius relation 



connects the specific heats and volumes of the superheated vapor, and 

 the Clapeyron equation 



a relation between the latent heat r, temperature, change of 

 volume IF" - J during vaporization, and the derivative .^ of the pressure- 



temperaturr function. 



A satisfactory formulation of the properties of a vapor therefore 

 involves two processes, i. The establishment of equations for the 

 various properties that represent accurately the most reliable of the 

 experimental data. 2. The correlation of such equations through the 

 thermodynamic laws. If such correlation can be- effected without sac- 

 rifice of accuracy, the resulting formulation will have the equally essen- 

 tial attributes, accuracy and consistency. 



The experimental evidence summarized in the preceding section is 

 sufficiently extensive and trustworthy to justify the conclusion that a 

 satisfactory formulation of the properties of water vapor may be worked 

 out ; and in the following sections is described the development of a con- 

 sistent theory that apparently gives with extreme accuracy the proper- 

 ties of superheated and saturated steam over a range of pressure and 

 ti-mjx-ratim- far wider than the range employed in technical applications. 



Pressures and Temperatures of Saturated Steam. - - The early ex- 

 periments of Regnault have been superseded by the recent experiments 

 conducted at the Rcichsanstalt. Each of the three series of experiments 

 conducted covered a different range of temperature. Scheel and Heuse's * 

 experiments covered the lower range 0-50 C. (32-i22 F.), Holborn and 

 Hcnning'st the range 5O-2OO C. (i22-392 F.), while Holborn and 

 Baumann's J experiments extended from 200 C. to the critical tem- 

 perature. 



The values of the saturation pressure as deduced from the respective 

 sets of experiments are given in the following tables. In the third table 

 the values are not those given by Holborn and Baumann but values 

 deduced therefrom by Prof. Marks. 



Annalen der Pbyric (4). VoL 31, pp. 715-735. 1910. 

 t Annalen der Phywk (4). Vol. 25. pp. 833-883, 1908. 



} Annalen der Phywk (4). Vol. 31, pp. 945-970, 1910. See alao articles by Risteen: The 

 Locomotive. VoL 26, pp. 85. 183. 246; Vol. 27, p. 54; Vol. 28, pp. 88, 118. 

 4 Proc. A. S. M. ., Vol. 33. P- 5 



