Mr Ramage, The Boiling Points of Homologous Compounds. 44*5 



The Boiling Points of Homologous Compounds. By Hugh 

 Ramage, B.A., St John's College. 



{Received 29 February 1904.] 



The relations between certain properties of elements and 

 their atomic masses have been described by the writer in Roy. 

 Soc. Proc, Vol. LXX. pp. 1 and 303, 1902. These relations were 

 discovered by a study of diagrams drawn with the physical 

 constants as abscissae and the atomic masses, or the squares of 

 these, as ordinates. This graphical method does not appear to 

 have been employed by other workers except in the simplest 

 form for showing that the properties are periodic functions of the 

 atomic masses. 



The method has been extended to other properties of the 

 elements and also to those of compounds. Amongst the latter 

 the boiling points offer the most complete data and in addition 

 furnish constants which are amongst the least affected by other 

 factors such, for instance, as association of the molecules, and 

 moreover they are, especially amongst organic compounds, the 

 most accurately determined of the physical constants. A study of 

 the boiling points of many substances has been made and some 

 facts relating to the boiling points of homologous compounds will 

 be dealt with in this paper. 



Professor James Walker has given a general formula, T=aM b , 

 for the boiling points of homologous compounds 1 in which T is 

 the boiling point in absolute degrees, M is the molecular weight 

 and a and b are constants for each series. He applied it to 

 several series and amongst them to the normal paraffins from 

 C 7 H 16 to C 16 H 34 . He found that it did not apply to the alkyl 

 bromides and iodides, the normal alkylamines, and the normal 

 ketones and aldehydes. He also stated that no formula of this 

 type could possibly be applied to the alcohols. 



It was observed when drawing the curve through the boiling 

 points of the paraffins that it would if produced below methane 

 pass very near to the position of hydrogen : it seemed at first 

 when using the older figure for methane (113°) that hydrogen 

 might be regarded as a member of the series. It was however 

 found by drawing a diagram with the logarithms instead of the 

 numbers that hydrogen did not fall on the curve but it fell near 

 it. The change from H 2 to CH 4 is not very different from what 

 it would be were hydrogen the first member of the series. 



In referring to the ten hydrocarbons to which his formula 



applies Walker remarked: — "In this particular case the formula is 



unusually simple, for the constant b becomes equal to 0*5, the 



curve of boiling points being therefore a true parabola." He does 



1 Trans. Chem. Soc. lxv. pp. 193, 725 (1894). 



