Affinity and Dissected (Structural) Formula. 421 



Affinity-values. 



Heat-disturbance. 



Marsh-gas +217 



Carbon dioxide 4-95-6 

 Formic acid ... 972 



Acetic acid 11 00 



Valeric acid ... 1495 



Butyric acid ... 146 3 



Palmitic acid... 2043 



+73-9 



-f43-8 



+463 



+63-3 



R , f + 82-6 and 

 Between j Ipn.i 



+97-6 



Methylic aleohol' 53-4 



Ethvlic alcohol..*. 637 



Amylic alcohol 86-2 



Butylic alcohol, between -j gg^ 



j Cetylic alcohol 1067 



The substances water and oxygen, however, form an exception 

 to this rule, inasmuch as the transformation of water, H 2 0, into 

 oxygen, O 2 , is attended with heat-absorption to the extent of 

 — 57*9; hence probably the rule of heat-evolution only applies 

 to the substitution of hydrocarbonous H 2 symbols. Unfortu- 

 nately there are no data for calculating whether such an opera- 

 tion as that symbolized by the formulae 



CH 3 



CH 3 



and 



CH S 



X CH 2 



where the two H symbols replaced belong each to a different 

 hydrocarbonous radical, is attended with heat-evolution or not; 

 but inasmuch as the boiling-point of the oxidized product (ethy- 

 lene oxide) is above that of the hydrocarbon (ethane), probably 

 heat is evolved during the operation (§ 36). 



33. In all the preceding cases the following connexion uni- 

 formly holds between the boiling-points and affinity-values of 

 any given pair of substances : — If an operation be performed on a 

 given substance such that the operation is accompanied by heat- 

 evolution (i. e. if the affinity-value of the product is greater than 

 that of the original substance), the boiling-point of the resulting 

 body (under 760 millims. pressure) is higher than that of the 

 original substance, and vice versa. 



Thus the increase of affinity-value in the ascent of an homolo- 

 gous series is well known to be correlative with an increase in 

 the numerical value of the boiling-point (Kopp). It deserves 

 notice that in the case of water and methylic alcohol and its ho- 

 mologues, where, as shown in §§ 27 and 31, there is heat- 

 absorption in the first stage (hydroxylic methylation), and heat- 

 evolution in each subsequent stage (hydrocarbonous methyla- 

 tion), the boiling-point is lowered by the first operation, and 

 raised during each successive operation. Thus : — ■ 



