153, 154] 



Isothermals 



135 



becomes more and more marked, so that in all substances the distinction 

 between the liquid and gaseous states becomes continually more pronounced 

 as we recede from the critical temperature. 



154. The following table gives corresponding values of p and v observed 

 at the critical temperature of isopentane, by Young*. This temperature 

 according to Young is 187'8C., the critical volume being 4'266 cubic centi- 

 metres for 1 gramme of the gas. The table is calculated by Dieterici'f' from 

 Young's observations. 



CRITICAL ISOTHERMAL OF ISOPENTANE. 

 Critical temperature = 187'8 C. Critical volume = 4'266 c.c. per gramme. 



To interpret this table, we revert to the general equation (303), 



p= R ^ p b e~^ T (312), 



where (cf. equation (304)) 



= p + V 2 + kp 3 + 

 in which b l} 6 2 ... are constants. 



* S. Young, Proc. Roy. Soc. xv. p. 126 and xvi. p. 11. 

 t Annalen der Physik, v. p. 58, 1901. 



.(313), 



