Dr Fyfe on the Illuminating Power oj Coal and Oil Gas. 367 
Raphia (Sagus) vinifera gives a beverage resembling wine, in 
Guinea and other places; Rice and the Sugar-cane furnish 
both Indies with spiritous liquors. 
Art. XXII. — On the Illuminating power of Coal-Gas , and Oil- 
Gas. Ry Andrew Fyfe, M. D. F. R- S- E., Lecturer on 
Chemistry, Edinburgh. 
In my paper, published in the last number of the Journal, I 
proposed the use of Chlorine, as a means of ascertaining the il- 
luminating power of the Gases derived from the decomposition 
of Coal and Oil. The few experiments I had at that time per- 
formed, left me rather undecided with respect to its accuracy. I 
have accordingly resumed the subject, and have found, that it 
promises to be not only one of the most accurate, but the easiest 
employed indication hitherto used. I have already stated, that 
oil and coal gas, after being properly purified, are nearly of the 
same composition, their ingredients being hydrogen, carbonic 
oxide, carburetted hydrogen, and olefiant gas, the last of which 
is almost the only source of light, and, in proportion as it va- 
ries in quantity, the illuminating power also varies. If this 
opinion be correct, we have merely to find the proportion of ole- 
fiant gas, and we have at once the relative power of illumination. 
The method I have described for effecting this is extremely 
simple. A graduated jar, inverted on a water-trough, must be 
filled to the mark 50 with chlorine, and fifty measures of the 
gas under examination then introduced, covering the jar with a 
paper shade, to prevent the action of light. In the course of 
about ten minutes the condensation is completed. As chlorine 
and olefiant gas combine in equal volumes, the diminution, 
indicated by the ascent of the water, points out the quantity of 
the latter in 100 of the gas. 
With a view of proving the accuracy of this method, after 
ascertaining the quantity of olefiant gas in different gases, I 
have tried their illuminating power in the usual way, and the 
results very nearly coincide. 
Exp. 1. — Gas prepared at the Edinburgh Coal Gas Works, 
from best parrot coal, was found to yield 17 per cent, of olefiant. 
Oil-gas, prepared at Mr Milne’s, from whale oil, yielded ex- 
actly 32 per cent. 
