THE THERMAL PROPERTIES OF STEAM 5 



Volume of Superheated and Saturated Steam. Characteristic Equa- 

 tions. - ct exj* i m the specific volume of saturated and 

 steam have been mac Kamsay and Young,* by Bat- 

 trlli.t . m l hy KnoNatiih, I. in.!.. .m<i Klrln-.J The experiments in the 

 Munich laboratory were ao superior in all respects to those of the other 

 im ;. .I-. !, that the result have been generally accepted. 



In conducting these experiments the volume of a predetermined 



: tram was kept constant and corresponding temperatures and 



prr>-nrr- \\rrr nh-M-rxrd. ih .,!.-. t\. d \.tiij. ol p nd ' vh B plotted 



a constant \.>lumr m .nh-.r" on the pi-plane. It was 



t<imd that thr curves, within thr limits of accuracy of thr experiments, 

 were straight lines. These lines were prolonged to intersect the satura- 

 tion rur\r />-/(/), and the points of intersection gave, therefore, stmul- 



>u- values of f>, r, and /, at thr saturation limit. 



For DOOM in rMaMi-hing a chara equation, Unde 



made use of the scheme of representation devised by Amagat. Values 

 of the product pv were plotted as ordinates against values of p as abscis- 

 sas. The experimental point- were not takm for this purpose but rather 

 thr point- drtrrmined by the intersection of the successive isochors by 

 lines of constant temperature. In this way the points on the pv-p plane 

 are separated into groups, each of which is associated with a particular 

 trmprruturr. In othrr words, curves through the successive sets of 



is are lines of constant temperature, or i*>thrrms. Fig. 2 shows 

 thr point- a- thu> determii 



Callendar in his paper on the properties of gases and vapors had 

 from theoretical con-i m deduced the characteristic equation 



r-6- -c ^Y' 



p C '\T) 



in \\hii-h b represents the minimum \ohiinr or co-volume of Him and 

 \an d-r \\'aaN. juation gives fair agreement with thr experimental 



\ahu-s at thr IO\M r trinprraturcs, hut it rrcjuirrs that the isotherms on 

 thr pv-p plane be straight lines, while the experimental points indicate 

 that they should have appreciable curvature. In Linde's equation 



the introduction of the term (i + ap) provides for the requisite curvaturr. 

 Tlu roulting isotherms are parabolas. 



\Yhilr 1. hide's equation represents the experiments very closely, it 

 is open to two serious objections, i. At 402 C. the "correction term" 

 changes sign. 2. The equation cannot be reconciled with the accepted 



Phil. Tran*. Roy. Soc. of London. Vol. i8j-A. p. 107 (1*92). 

 t Annales de Chimic ct dc Ph>-mique (7). Vol. J. p. 4<* (i*94>- 

 I Mitteilungen Ober Fonchungnrbeit.. Vol. 21. pp. 33-72 (1905). 

 5 Proc. of the Roy^l Soc. of London. VoL 67 (1900). pp. 266-286. 



