SPECIFIC HEAT OF AMMONIA, 393 



where T denotes absolute temperature, as distinguished from Q which 

 is used to denote the usual Centigrade scale. 

 Substituting (1) and (26) in (25) and solving for c^ 



■ S2» 



Cs2 ^V\2 "I 





By use of Equations (26) and (27), the specific heats along the 

 boundary line of the liquid vapor region shown in Figure 2, can be 

 computed, when the experimentally determined values of c„i2 (Table 

 II), and the thermodynamic quantities, L, I'l and V2, are given as 

 functions of the temperature. 



In Equation 27, v denotes the specific volume at which Cv^o was meas- 

 ured. But from values of c^jj as a function of the temperature at some 

 one particular specific volume, the values of c^^^ at any other specific 

 volume can be computed. Let the volume at which the measure- 

 ments are made be denoted Va instead of v, and let the specific heat 

 at this specific volume be c^a where the subscripts i and 2 are under- 

 stood. Similarly, let Cn be the specific heat of the liquid-vapor 

 mixture at the specific volume r^. To obtain an equation connecting 

 Cva and Cvb, wTite Equation 27 twice, once using (",,„ and Va, and again 

 using c^.b and Vb. Subtracting these two and rearranging 



Further, the specific heat along any path whatsoever, ^^ may be 

 written 



'dp\ dv ^29) 



dv 

 where p is the pressure and — - depends on the path. 



di 



These equations, (26), (27), (28) and (29), show that the specific 

 heat along any path in the liquid-vapor region, and along the bound- 

 ary of that region, may be computed from values of the specific heat 

 along some one constant specific volume line in that region. Such 



16 Reference (3) p. 5. Modification of Eq. 10. 



