124 



Mr. Bosanquet on the Illuminating-Power 



Again, lines drawn through the points representing the 

 two sets of mixtures, excluding the ethylene point, meet at a 

 lower C.P. than that given by the direct determination of 

 ethylene. 



A value of 65 C.P. for ethylene fits both series much 

 better than the direct number 68'5, and would also fit better 

 combinations which occur later. 



I therefore adopt the number 65. The question is here 

 not so much whether this is the exact C.P. of ethylene, as 

 whether the mixtures behave as if it were so. This they appear 

 to do. 



The remaining mixtures are all made with " disill unlimited 

 gas " of the Gas Light and Coke Company. The analysis of 

 this gas is given at Chem. Journ. 1884, p. 193. The C.P. 

 of the original gas is 16. I assumed at first that the " dis- 

 illuminating " was equivalent to the removal of the heavy 

 hydrocarbons, the proportions of the remaining marsh-gas 

 and hydrogen giving the value of x. I did not take any 

 account of the presence of the other gases, which include 

 about 6 p. c. of nitrogen and 4 p. c. of carbonic oxide. 



The percentages of hydrogen and marsh-gas are 



H 2 =47-99, CH 4 =37-64. 



From these the C/H ratio comes out x = '1527, as obtained 

 direct from the analysis. 



Two mixtures were made with this disillumiuated gas and 

 ethylene * ; I have added the values of x. 



Disillutninated 

 gas. 



Ethylene. 



X 



C.P. 



y 



1684 



2840 



86-59 

 68-98 



1341 

 3102 



•2224 



•2992 



These points are represented in the figure by upright 

 crosses, + ; a line drawn through them passes below the 

 ethylene point at 65, and to the left of the calculated dis- 

 illuminate point # = '1527. It must be remembered that, 

 besides the possibility of imperfect disillumination, the gas 

 contains considerable quantities of nitrogen and carbonic 

 oxide ; so that it seems better to derive the disilluminate 



* Z. c. p. 191. 



