40 THE TRUE VALUE OF a OF VAN DEK. WAALS' 



The latent heat values are again higher than the others. The 

 mean is 21.30. This is in fair agreement with the value 21.46 required 

 by the computation from the weight and valences, taking as in 

 the other cases 28 valences. Van Laar's value for a v ' 2 is .213, 

 from which a is computed as 19.91 X 1 ()12 . This a § ain 1S (lc,i " 

 dedlv below the true value. 



20. Carbon tetrachloride. CCl±. 



(a), a = 2.03 ET c K/l.0S - P C K 2 - T a = 550.15 ; P, = 34.181; 

 dr = _ 557(5 ; /; = 275.8. M = 153. S a = 21.68 X I0 ,a 



{b). a = Q:5P c K 2 ..... "•• a = 22.51XI0' 2 



(c). fl=/Jf»/a^. /*' = 44.29 «=153.8. a = 21.57 XI©" 



(,/).♦ a = G'BT e V c . G = 1-007 a . = 21.27 X 1© ,S 



[e). a = 3 sv^ MN 113 T* %d - - B) (?', — Tf\ 

 Walden and Swinne at 21° s = 25.85 

 dvnes; sy 2/3 = 544.91 ergs. .'/',. — T = 

 202.15°. d= 1.5920: D disregarded, a ,= 22.06 X I©' 2 

 The mean of these values for a is 21.82 X l© 2 This is in good 

 agreement with the computation from the molecular weight and 

 number of valences, counting chlorine as trivalent so that there are 

 10 valences in the molecule, of 21,14 X 10' 3 . Van Laar's value 

 corresponds to 19.09 X i()12 - Lewis calculates from the latent heat 

 of expansion of the liquid a still higher value of 22.04 X J ° 12 - 



27. Hexametliylene. C 6 if 12 . 



(a). « = 2.03 #7^/1 .03 — P C V*. P c == 80.260 *»;«./fy; T c = 



553; d e =. 2735; F c =307.1 a = 24.04Xl©' 2 



0). a = 6.5 P C V* a = 21.73 XI© 12 



( C ). « =/ /J/^;3r/X ! . J/=si; //= 103.03.. a = M.21XW" 

 (d). a = C'BT C V C . C' = 1.694 a = 23.94 X l© 2 



(6'). Surface tension not found. 



These values agree pretty well. The mean is 21.23 X Ï©' 2 - This 

 is in excellent agreement with the value calculated from the mole- 

 cular weight and number of valences of 24.30 X 1©' 2 > there bein S 

 36 valences in the molecule. 



Van Laar's value is, for a 1/ ;, .211, which corresponds to 

 19.53 X 10l2 > ;1 value wnicn ls much too low. His computed value 

 is still lower. 



