INTRODUCTION. 2$ 



lessor Thomas's diagram giving mean specific heats, specific beau at 



various t< ires and at a given pressure were obtained, and the 



thu> ni.t.im. -1 v.rre faired after a comparison with curves cou- 



rt! with Professor Knoblauch's specific heats at those temperatures. 

 These curves were then integrated graphically and the results checked 

 by comparison with his mean specific heats. 



ropy. By the entropy of superheated steam is meant the increase 



of mi ropy due to heating water from freezing-point to the temperature 



of saturated steam at the given pressure, to the vaporization and to the 



ing at that pressure. This operation may be represented as 



follows: 



in which T is the absolute temperature of the superheated steam, and T t 

 i> the icm|*Tature of the saturated steam at the given pressure; and *- 



can be taken from Table I. The last term was obtained for the tcm- 

 peratim -entropy table by graphical integration of curves plotted with 



values of ^ derived from the curves of specific heats at various tempera- 



>t described under the previous section. 



Properties of Sulphur Dioxide. One of the most interesting and 

 imjx>rtant appliiations of the theory of superheated vapors is found in 

 the approximate calculation of properties of certain volatile liquids which 

 .-eel in refrigcrating-machine-. and for which we have not sufficient 

 experimental data to construct tables in the manner followed for the 

 fluids already discussed. 



All attempts in this line have followed the example of Lcdoux. who 

 made the first attempt and who naturally took for the basis of his r 

 tigations the form of equation proposed by Zcuner for superheated steam, 

 nam 



pv - BT - Cf. 



Investigations by Knoblauch already discussed show that this equation 



can be considered only a crude approximation for steam, and conse- 



quently less confidence can be placed on investigations by its aid than 



rmerly thought. Nevertheless, in our present condition and until 



more complt mental data are available we are constrained to 



