466 



Transactions. — Chemistry and Physics. 



Acid. 



Acetic . . . 

 Propionic 

 Butyric ... 

 Valeric ... 

 Hexoic ... 

 Heptoic . . . 

 Laurie . . . 

 Stearic ... 



Table I. 



No. of Carbon Atoms Association 



in Molecule. Factor. 



2 100 



3 1-01 



4 1-03 



5 105 



6 106 



7 1-07 

 12 1-11 

 18 1-01 



On the other hand, the rate of association alternately in- 

 creases and decreases ; thus in this case there is an intimate 

 relationship between the attainment of maximum association 

 and the wavy nature of a closely related property. 



Generally speaking, association decreases with rise in mole- 

 cular weight. This was observed by Eamsay and Shields and 

 by Traube in the case of liquids, and is also true for the 

 association of the fatty acids in the gaseous state as measured 

 by their vapour densities.* An increase of molecular com- 

 plexity which extends to far up the series, as in the case of 

 the aliphatic acids in phenol, has never been previously ob- 

 served. 



(2.) When the Compounds are in the Liquid State. — Ex- 

 amples of this are exceedingly numerous for the rotary power 

 of optically active compounds. Guye showed that in many 

 cases the explanation may be given from his hypothesis of the 

 product of asymmetry. Frankland,f on the other hand, ex- 

 plains the maximum or minimum in many cases as due to the 

 association of the initial members of the series. A clear case 

 of this is exhibited by the esters of active amyl alcohol (Guye 

 and Chavanne). The association factor is calculated accord- 

 ing to Traube 's formula : — 



Table II. 



Ester. 



Amyl formate 

 acetate 

 propionate 

 butyrate 

 valerate 

 hexoate 



+ 

 + 

 + 

 + 

 + 

 + 



[a]. 



201 

 2-53 



2-77 

 2-69 

 2-52 

 2-40 



Association 

 Factor (15°). 



108 



1-02 



100 



0-94 



0-92 



0-90 



Here it is seen that when there is no association the values 

 of [a] regularly increase. 



* Easterfield and Robertson, Trans. N.Z. Inst., 1901, 499. 

 t Trans. Chem. Soc, 1899, 347. 



