24 PROPERTIES OF STEAM AND OTHER VAPORS. 



one third of one per cent. Exterpolated results are probably less reliable 

 than those obtained directly by Professor Thomas. 



The following table gives the mean specific heat of superheated steam 

 as measured on a facsimile of Professor Thomas's original diagram without 

 exterpolation. 



SPECIFIC HEAT OF SUPERHEATED STEAM. 

 Thomas and Short. 



Here again the arrangement of the table can be made evident In an 

 example: Required the heat needed to superheat steam 100 degrees at 

 200 pounds per square inch absolute. The mean specific heat from 

 saturation is 0.55?, so that the heat required isgO.f thermal units. 



Total Heat. In the solution of problems that arise in engineering 

 it is convenient to use the total amount of heat required to raise one 

 pound of water from freezing-point to the temperature of saturated 

 steam at the given pressure and to vaporize it and to superheat it at that 

 pressure to the given temperature. This total heat may be represented 

 by the expression 



where / is the temperature of the superheated steam, /, is the tem- 

 perature of saturated steam at the given pressure />, and q and r are 

 the corresponding heat of the liquid and heat of vaporization. The 

 mean specific heat c f may usually be selected from one of the given tables 

 without interpolation, as a small variation does not have a very large 

 effect. 



The total heats or heat contents of superheated steam in the tempera- 

 ture-entropy table were obtained by the following method. From Pro- 



