446 



Mr Ramage, The Boiling Points 



not discuss the point further. The curve to Walker's formula 

 was drawn on the diagram and in studying the two curves it 

 appeared probable that the simple formula only applied exactly to 

 the CH 2 chain linkage and that the influence of the terminal 

 hydrogen atoms was either a constant in the higher members of 

 the series or it was so small that it might be disregarded. The 

 influence of these terminal atoms increases as the chain shortens 

 and the atoms approach each other until in methane the diagram 

 indicates we practically have the effect of two CH 2 groups. This 

 work has suggested a modification of the formula which applies to 

 the series from methane to hexadecane. 



The new formula is T=a [M (1 — 2 _n )p, where n is the 

 number of carbon atoms in the molecule. The constant a is 

 the same as Walker used. It may however be expressed as a 

 function of the pressure and it is given approximately for pressures 

 of 15, 30, 50, 100, and 760 mm. by the equation <x = 23-5P' 07 , 

 where P is the pressure. Calculated from the first sixteen 

 members of the series for a pressure of 760 mm. its mean value 

 is 37'3775, a figure which is practically identical with that cal- 

 culated by the simpler formula (37 '38) from the higher members 

 of the series. When n = l\ and upwards the two formulae give 

 the same results to the first decimal place. The following table 

 gives the observed and calculated numbers and the differences 

 between them. 



