Dr. Andrew Fyfe on the Comparative Value, fyc. 77 



Art. VIII. 



for the purpose of 



of different Kinds of 



hitherto practised for ascertaining the Value of the Gases they 

 afford; by Andrew Fyfe, M.D., F.R.S.E., F.R.S.S.A., Pro- 

 fessor of Chemistry King's College University, Aberdeen, &c. 

 Read before the Royal Scottish Society of Arts, April 24, 



1848* 



In a paper published in the Transactions of the Society for 

 1842, I gave an account of numerous trials made with the view 

 of ascertaining the value of different kinds of coal for the pur- 

 poses of illumination. Having been again engaged in conducting 

 experiments for the same purpose, I have been induced to make 

 some of the results public, because I conceive that they are in- 

 teresting, and lead to valuable practical applications. 



The objects which I have had in view were to ascertain not 

 only the comparative amount of light afforded by the gases which 

 the coals yield, but also the durability of these gases, so as to en- 

 able me to fix, as far as possible, their comparative value, and, 

 consequently, their comparative expense, for the purpose of illu- 

 mination. Besides these, however, my attention was drawn to 

 other circumstances connected with the consumption of gas, 

 which, strictly bearing on the other part of the inquiry, are of 



importance. 



1. Quality of 





In estimating the quality of coal-gases, and, consequently, 

 fixing their comparative value for the purpose of illumination, 

 we must take into account both the light afforded, and the time 

 required for the consumption of equal volumes. 



In trying the former, I have, in the following experiments, in- 



variably had recourse to the method mentioned in my former 

 Papers, viz., the condensation by chlorine, and in which, now 

 that the trials have been greatly extended, I place the utmost 

 confidence. 



For ascertaining the latter, I have followed the usual method, 

 an accurately-adjusted experimental metre ; by which the times 

 required for the consumption of equal volumes, burning under 

 similar circumstances, and also the quantity consumed in equal 

 times, were easily determined. The jet burner was the same in 

 all the trials. 



I consider both of these circumstances absolutely necessary, 

 for, though some have insisted only on the one, and others on 

 the other only, yet, unless both be taken into account, we do not 



* From Jameson's Jour., Edinburg, vol. xlv, pp. 37—49 





