10 



PROPERTIES OF STKAM AND AMMONIA 



merits at least as well as the other systems, (2) gives more probable 

 values of c 9 at saturation, and (3) gives more trustworthy values of c p at 

 high temperatures. 



Regnault's measurements of c, at atmospheric pressure may be used 

 as a rough check on corresponding values calculated from Eq. (C). The 

 four series of experiments covered the temperature range I22.8-23I.I C. 

 The mean value of c, given by Regnault was 0.4805, but thi> \.ilue is 

 lowered to 0.4762 by Davis. All experiments were conducted at atmos- 

 pheric prcssim . The following table gives values of c p at atmospheric 

 pressure calculated from the equation, also the values assigned by Jakob 

 for the slightly lower pn ->ure. i kg. per sq. cm. 



SPECIFIC HEAT AT ATMOSPHERIC PRESSURE 



The mean c 9 deduced from the equation agrees very well with the 

 recomputed value 0.4762. 



Heat Content of Superheated and Saturated Steam. From the two 

 laws of thermodynamics the following general equations are derived. 



In the second equation we introduce the expression for c p given by 

 (C) and the expressions for f } and v obtained from the character- 



i>tir equation (B). The result of the substitutions is the exact differen- 

 tial equation 



which upon integration gives the following equation for the heat content, 



. (D) 



The constant i* is determined as follows. Corresponding saturation 

 values of p and / at some definite temperature, say 212 degrees, are sub- 

 stituted in the equation, which for this purpose may be written 



The function 4 (p, T) is thus calculated, and i^ being known, ^ is found 

 by subtraction. The value 4, * 948.54 B.t.u. is thus determined. 



