58 



THE TRUE VALUE OF a OF VAN DER WAALS' 



TABLE 2a. 



Values of a in atmospheres and for a volume containing the 

 same number of molecules as 1 c.c. of a gas at 0° C. and 760 mm. 

 pressure. The values in this table are obtained from those in Column 8, 

 Table 2, by dividing the latter by 4.923 X 10 14 - One atmosphere 

 being 1.0132 X l^) 6 er g s f° r a c.c, and the number of molecules 

 in a gram mol being 6.062 X ^' 23 an ^ m ^c-c- of a gas under 

 standard conditions 2.75 X 10 19 , (6.062 X 10 23 /2.75 X 10 19 ) 2 X 

 1.0132 X 1° 6 eq ,ials 4.923 X 1()U - 



Hydrogen 0006053 



Nitrogen 00349 1 



Oxygen 003819 



Carbon monoxide. . . .003494 



Methane 006073 



Nitrous oxide 008714 



Carbon dioxide 008714 



Acetylene 009730 



Ethylene 01156 



Ethane 01341 



Chlorine 01497 



Sulfur dioxide. ..... .01530 



Methyl formate 02325 



Bromine 02576 



Carbon bisulfide 02722 



Methyl acetate 03307 



Ethyl formate 03307 



Ether 03884 



n-Pentane 0416s 



i-Pentane 04168 



Benzene 04211 



Fluor benzene 04836 



Ethyl acetate 04359 



Propyl formate 04359 



Methyl propionate 04359 



Carbon tetrachloride... .04355 



Hexamethylene 04936 



n-llexane 05261 



Diisopropy] 05261 



Chlor benzene 05610 



Methyl butyrate 05478 



Methyl isobutyrate 05478 



Propyl acetate 0547s 



Ethyl propionate 05478 



Stannic chloride. ..... .06175 



n-Hcptane 06415 



Brom benzene 06713 



n-Octane 07625 



Diisobutyl 07625 



Iodo benzene 07991 



Mesitylene 07682 



Cymene 08944 



Diisoamyl 10197 



Diphenyl methane 11645 



Having these values all before us we may compare them in 

 Table 2 and thus see whether the values computed from the 

 molecular weight and the number of valences by the formula: 

 a = N 2 (jn?Jc X ValjMf* do, or do not, agree closely with the 

 values found from the surface tension, from the internal latent 

 heat of vaporization and from the critical data on the basis that 

 a = 6.5 P C V C 2 . The values computed from the gravitation and 

 valences are in column 8 and right alongside of them in column 



