EQUATION AND THE NATURE OV COHESION. 



23 



Sn OL. >S = 3.755. 



T 



3 7:') 

 423 

 473 

 513 

 533 

 553 



L 



31.70 

 28.35 

 24.57 

 20. Sö 

 18.50 

 15.60 



d 

 2. 01 SO 



1 



8772 

 7224 

 5007 

 4747 

 3628 



I) 



.0057 1'/ 

 .02023 

 .05459 

 . 1083 

 . 15 20 

 .2160 



C 



7.18 

 7 . 3 I 



; . 13 



7.52 

 7 . 5 I 

 7 . 50 



An examination of the foregoing ligures shows that the equation 

 of' Crompton is not entirely true, for in general the value 8LJHT 

 L//UI/D) is never in any substance quite constant, but in all it 

 shows a fairly uniform course, being somewhat lower at the lower 

 temperatures, rising to a maximum and then declining again near 

 the critical temperature. In a few substances it is more constant, 

 namely in iso-pentane, pentane and benzene. These are the sub- 

 stances, to be sure, of which the density is most accurately known. 

 On the whole, however, the equation is approximately tine. The 

 value of the constant comes very close in many substances to the 

 expected value of 7.5 and this in widely different substances, 

 ranging from benzene, to nitrous oxide and carbon dioxide, in 

 octane, methyl butyrate and methyl acetate it is somewhat higher 

 ranging in octane from 7.70 — 8.38. On the other hand >S0 2 is 

 lower than it should be. With these exceptions the agreement is 

 certainly fair with our expectation and shows that the ratio of 

 K c jP c must be nearly, if not exactly, 6.5 in triatom'ie gases as 

 well as more complex substances. There is no indication, 1 think, 

 of any general trend in the constant with an increase in molecular 

 complexity. Pentane is little if any higher than N 9 0. The evidence 

 from this source bears out, then, the determinations of the ratio 

 of KjJP c from the ratio of the total to the internal latent heat 

 near the critical temperature. 



It ought also to be true, if the foregoing is true, that near the 

 limit of the critical temperature 



L 



1\V- 



,T dlK 

 ■v)~~\PdîV c 



r e *p.-Ki 



7.5 



(U 



At the critical temperature this ought to be equal to 7.5, but on 

 testing this on two or three substances, the ratio L -. P{V — v) was 



