﻿590 Mr. D. L. Hammick on Latent Heats 



2 lamberts. Doubtless some function of the intensity and 

 the angle could be devised such that, in a corresponding 

 sense, one candle-power per square centimetre would be 

 equal to ix lamberts, but we cannot discover a function 

 which has the least intrinsic plausibility. Doubtless the 

 American committee have succeeded where we have failed, 

 but they have been unduly , modest in concealing their 

 ingenuity ; they ma} r fairly be asked to explain how they 

 have arrived at their surprising result and why they have 

 preferred it to the simple and obvious convention which 

 gives the result that 1 candle-power per square centimetre 

 equals 1 lambert. 

 May 27, 1922, 



A 



LIU. Latent Heats of Vaporization and Expansion. 

 By D. L. Hammick*. 



C CORDING to van der Waals, the pressure in a 



homogeneous fluid system is p+— 2 . When the 



system expands, work is done against the pressure. The 

 value of this work for the expansion of 1 gram of a liquid 

 (volume vi c.c.) until its volume is v 2 cc, the specific 

 volume of the liquid when completely vaporized, is 

 given by 



= I pdv + I 



cK Jt-i 



a j 



~ 9 dv 



a a 

 V, v 2 



When r 2 is large when compared with r 1? this expression 

 becomes 



or, putting pv 2 equal approximately to 



A - M i h 



M 



RT a 



(1) 



* Communicated by the Author. 



