Temperature, and Volume in Saturated Vapours. 307 



The latent heat of vaporization has hitherto been expressed 

 only in terms of the temperature by the empirical formula 



L = 796-23-0-695*, (10) 



where t is the absolute temperature, and the smaller terms 

 containing higher powers of t are omitted. From the rela- 

 tion between p and t we get 



894 

 L = 799--^F— — (10a) 



(a-logiO* 



t 



p. 



L. 



From 

 Zeuner. 



By equation 

 (10). 



By equation 

 (10 a). 



273 

 323 

 373 

 423 

 473 



4-60 

 91-98 

 760-00 

 3581-2 

 11689-0 



606-5 

 571-8 

 537-0 

 502-3 

 466-5 



607-0 

 571-7 

 536-3 

 501-0 

 465-9 



606-5 

 571-7 

 536-5 

 500-8 

 464-3 



The new formula (10 a) is more accurate than the one (10) 

 commonly used. 



Let v be the volume in cubic metres of a kilogram of steam, 

 and s the volume of the same quantity of water, usually taken 

 at 0-001, 



t7-*=10-821 



p?(a-\ogpy 

 where p is still expressed in millimetres. 



(ii) 





V- 



■s. 



p. 







By equation (11). 



From Zeuner. 



4-60 



208-7 



210-6 



91-98 



12-14 



1205 



760-00 



1-652 



1-650 



3581-2 



•3833 



•3839 



11689-0 



•1255 



•1257 



Other Vapours. 



The following equations may be useful. That for ether 

 agrees extremely well. The mercury equation less well ; but 

 the errors are considerably less than those of Rankine's equa- 

 tion in his paper of 1850. The data are all from Regnault. 



Z2 



