2 Dr. S. Young on the Boiling-Points 



molecules tend to associate together ; moreover, the esters, 

 which are formed by the interaction of alcohols and acids, 

 do not behave quite normally, and there is probably molecular 

 association, though to a much smaller extent than with the 

 hydroxyl compounds. There can be little doubt that if 

 Kopp had been able, in the first place, to obtain a considerable 

 number of pure substances of normal behaviour, such as the 

 paraffins or their halogen derivatives, he would not have 

 been led to the erroneous conclusions which he defended 

 with such vigour for so many years. 



Taking the normal paraffins as the simplest class of organic 

 compounds, it is found that, instead of the boiling-points 

 rising by equal intervals as the series is ascended, the rise, 

 which is very large for the lowest numbers, becomes smaller 

 and smaller as the molecular weight increases. This fact is. 

 of course, now well known, and various formula? have been 

 proposed to reproduce these boiling-points. 



Thus, Walker has proposed the formula T=aM 6 , where T 

 is the boiling-point on the absolute scale of temperature, M 

 is the molecular weight, and a and b are constants. Ramage* 

 last year suggested that this formula applies only to the 

 (>H 2 chain linkage, and that the influence of the terminal 

 hydrogen atoms is considerable in the case of the lowest 

 members, but diminishes as the chain lengthens, and becomes 

 eventually either constant or negligible. In other words, 

 the lower members of the series cannot be regarded as truly 

 homologous, and that is a point which is, I think, important 

 to bear in mind. Ramage suggests a new formula, 

 T=a[M(l~2- TO )p, where a is Walker's constant 37-3775, 

 and n is the number of carbon atoms in the molecule. He 

 assumes, however, a constant difference for CH 2 in the case of 

 the alcohols, the aldehydes, and the ketones, but it is doubtful 

 whether the boiling-points of the last two classes of com- 

 pounds are yet sufficiently well established to allow of any 

 certain conclusions being drawn from then?. 



It may be useful to regard the rise of B.P. for an incre- 

 ment of CH 2 as being mainly a function of the absolute 

 temperature, and the formula 



A _ 144-86 



r J[ 0-0148 VT 



(where A is the difference between the boiling-point, T, of 

 any paraffin and that of its next higher homologue) may be 

 provisionally adopted. Taking the boiling-point of methane 

 as 106°* 75 abs., the values for the higher members agree 

 better with the observed temperatures than those given by 

 Ramage's formula, as will be seen by the following table. 

 * Cambridge Phil. Soc. Proc. xii. p. 445 (1904). 



