122 Mr. Bosanquct on the Illuminating -Power 



In addition to these we have also from P. Frankland * : — 



Ethane, C 2 H 6 

 Propane, C 3 H 8 



Carbon 

 Density. 



2 

 3 



C/H ratio. 

 i 



•375 



C.P. 



35 

 54 



These were all laid down as on the figure. These mixtures 

 are shown by round black points ; ethane and propane by 

 oblique crosses, x . 



The general course of the mixtures can be roughly repre- 

 sented by a straight line. This, however, passes below the 

 ethylene point at the top. All the mixture lines obtained 

 later agree in placing the ethylene point at a C.P. lower 

 than 68*5, and we shall assume that 65 is the point through 

 which the line should be drawn. 



The point representing ethane lies on the right of the line, 

 below it, and near it at a point whose carbon density is about 

 1, that of ethane being 2. The point for propane is on the 

 other side of the line, its carbon density being 3. It appears 

 then that, so far as mixtures are concerned, the carbon density 

 has no direct influence. The influence of carbon density on 

 pure substances will be treated later. 



Next we proceed to consider the mixtures of ethylene and 

 marsh-gas given by P. Frankland, I. c. The carbon density 

 is now omitted. 



Ethylene and Marsh- Gas. 



C 2 H 4 . 



CH,. 



C/H ratio. 



X 



C.P. 



y 



85-67 



1433 



•4642 



5791 



6909 



30*91 



•4227 



47-88 



5774 



42-26 



•3943 



4042 



35-90 



6410 



•3397 



3317 



1300 



S7-00 



•2825 



19-35 



7-87 



92-13 



•2697 



1759 



These are also laid down on the figure, being represented 

 by small circles with dots in the centre. It will be seen that 

 they lie pretty closely upon a straight line drawn from the 

 point which represents ethylene, taking the C.P. as 65, and 

 meeting the x axis, or disilluminate line, at x — *19 nearly. The 

 last two terms of the above series afford an explanation which 



* Chem. Journ. 1885, p. 238. 



