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XL. On the Calculation of the Illuminating-Power of Hydro- 

 carbons and their Mixtures, — Part II. Diluents, and 

 general second approximation. By R. H. M. BoSANQUET, 

 F.E.S. 



[Continued from p. 130.] 



FOR the purpose of considering the relations of diluents 

 to the illuminating-power of hydrocarbons, I shall 

 modify the definition of the quantity x, the C/H ratio of the 

 last paper. I shall regard the hydrogen as only one of 

 a class of diluents, whose chief function is to occupy a certain 

 volume, while they are also capable of holding certain pro- 

 portions of carbon in quasi-solution, and withdrawing it from 

 precipitation in the flame. I shall call x the carbon/ diluent 

 ratio. It is the ratio of the volume of carbon vapour present 

 to the sum of the volumes of the diluents. The following 

 embodies the rules I have employed in calculating x. 



Then 



Let there be a proportions of hydrocarbon C m H„, 

 „ b „ element H 2 or N 8 , 



„ c „ neutral gas CO or C0 2 . 



ma 

 x = 



?ia + 2b + 2c 



For the hydrocarbons and elements, we suppose them 

 pulled to pieces, and the atoms counted, for the purpose of 

 estimating the proportions. The numbers of atoms will be 

 proportional to the volumes of the substances in the free 

 state. Neutral gases, behaving more or less in the manner of 

 hydrogen or nitrogen, are reckoned as if they were elements. 

 This representation is only concerned with the volumes of 

 the substances. Their properties are indicated by other 

 means, x thus arrived at is the volume of carbon vapour in 

 unit volume of diluents. 



It must be observed that while the values of x employed 

 in my previous paper for hydrocarbons and their mixtures 

 remain unchanged, in cases where diluents are concerned, as 

 in coal-gas and disilluminated coal-gas, the values of x to be 

 now employed will differ materially. 



The following tables embody the experiments of P. Frank- 

 land on mixtures of diluents with ethylene, the values of x 

 being added. The figure represents them graphically. 



