0-0 Attraction Constant of a Molecule of a Substance. 



also to the benzenes in the table. Tt does not seem possible 



T fl 



to draw any further conclusions from the values of — - in 



the table. 2 ^ m i 



Ir will in general be found that if the molecules of a com- 

 pound contain the same atoms as the molecules of another 

 compound and in addition to these one or more atoms of any- 

 kind, the value of _-/ — of the former compound is always 

 smaller than that of the latter. 



(i< neral Remarks, 



T 

 The valnes of — — or P of substances, where T denotes 



a corresponding temperature, may be expressed in terms of 

 other quantities. Thus from equations (1), (2), (3), (4), and 

 (5) we have 



p_ II J^_ H 2 j* 



' i; '^ ,«/ M-^v v//iU i/7- 



/n\ 4 / 3 



At corresponding states each of the quantities ( ) %y/m l9 



7< / =\I/3> 7^-7 — r, .^r-/-— f 7 ' 1S ec l ual to P multiplied by 



a constant whicti is the same for each substance, and these 



T 



quantities therefore possess the same properties as j_— . 



The theory of corresponding states is, however, only ap- 

 proximately true, and the properties of these quantities may 



therefore not appear so marked as those of j=~» 



rp Xvm 1 



The properties of the quantity — or P of substances, 



we have seen, usually run parallel with the chemical properties. 

 One of these, stated in general terms, is, if (£(H, C, 0,...) 

 denotes the general chemical formula for a group of sub- 

 stances linked together by chemical properties, then the 



T 



equation A — </>(H, C, 0,...) = =-, where A is a constant, 



\*Jm x 

 applies to all the substances. The various results obtained 

 indicate the lines along which chemical compounds may be 

 classified according to their physical properties. They would 

 also be of use in aiding the classification from a purely 



