Revieivs and Notices of Boohs. 



133 



a single gas, but a mixture of several, of which the following may 

 be considered as a pretty complete enumeration : — 



Hydrogen .... 



. H. 



Marsh Gas .... 



. C^H,. 



Olefiant Gas .... 



. C,H,. 



Butylene (Oil Gas), traces 



. CgHg. 



Carbonic Oxide 



. CO. 



Carbonic Acid 



. CO,. 



Sulphide of Hydrogen 



. HS. 



Ammonia .... 



. NH3. 



Nitrogen .... 



. N. 



Cyanogen, a trace . 



. NC,. 



Vapour of Water . 



. HO. 



J, of Bisulphide of Carbon 



. cs,. 



„ of Benzole . 





*' The determination of the exact composition of a coal gas is a 

 task of considerable difficulty ; but if the ammonia, carbonic acid, 

 and sulphide of hydrogen be first removed, its analysis may be 

 accomplished in the following manner : — 



" 1. The oxygen is absorbed by a ball of papier-mache soaked 

 with an alkaline solution of pyrogallic acid. 



" 2. The heavy hydrocarbons, or luminiferous constituents, are 

 next condensed with absolute sulphuric acid in the manner already 

 explained. 



" 3. The residual gas, which is a mixture of hydrogen, marsh 

 gas, carbonic oxide, and nitrogen, is burned in a eudiometer with 

 a known volume of oxygen, the quantity used being more than is 

 sufficient for the conversion of their carbon into carbonic acid, 

 and their hydrogen into water, and the volume left accurately 

 measured. A ball of hydrate of potash is then introduced into 

 the tube, and the diminution of volume noted, — which corresponds 

 to the volume of carbonic acid produced by the combustion of the 

 marsh gas and carbonic oxide. 



" 4. There now remain but the nitrogen of the coal gas and 

 any excess of the oxygen used for the combustion. The latter is 

 got by adding at least 2 volumes of pure hydrogen, again explod- 

 ing in the eudiometer, and noting the condensation. This divided 

 by 3 will be the volume of the oxygen in excess, and of course 

 the nitrogen and the oxygen consumed are had by difference. 



" 5. The aggregate of the oxygen in the gas, its nitrogen, and 

 the heavy hydrocarbons, is now subtracted from the volume of 

 gas with which the experiments were begun, and a residue is 

 obtained representing the sum of the volumes of the hydrogen, 

 marsh gas, and carbonic oxide. Let the bulk of this sum in cubic 



