FORiMATION OF COAL AND CARBONACEOUS MINERALS. 131 



of inventors have proposed processes, and have taken out patents 

 for tlie conversion of tlie comparatively low value fatty hydro- 

 carbons into the higher value aromatic ones by passing the vapours 

 through heated tubes and otherwise, none of these have been 

 commercially successful in consequence of the loss being great in 

 the form of lower fatty hydrocarbons, and the yield of aromatic 

 therefore small. 



The Cg formula of celulose has been thought to connect it with 

 the aromatic series, but all transformations convert it into hydro- 

 carbons, alcohols, and acids of the fatty series. On the other 

 liand ligno-cellulose as found in jute, and other bast fibres with 

 a higher percentage of carbon and a lower of oxygen does yield 

 aromatic compounds — as hippuric acid during its digestion by 

 herbivorea — and by its giving pyrocatechuic acid by chlorination, 

 and subsequent treatment of the chlorinated product by fusion 

 with potash. Ligno-cellulose, however, treated with nitric and 

 sulphuric acids yields no aromatic nitro-derivatives, so that the 

 benzine nucleus must be absent. This seems to connect ligno- 

 cellulose with these coals which do not yield valuable aromatics 

 during distillation, that is cokeing, steam, and splint. I do not 

 enter further into the consideration of those coals at present. 



Suberose, cutpse, or adipo-cellulose, the principal constituent of 

 cork and the cuticular envelopes of plant tissues, difters widely 

 from ordinary cellulose and yields by all treatments substances 

 belonging to the fatty series, and it seems probable that if trans- 

 formed into mineral coal it would retain its fatty character. 



Published analyses of these three celluloses shew the following 

 numbers : — 



Cellulose. Ligno-cellulose. Adipo-cellulose. 

 Carbon 44.6 ... 47.0 ... 73.66 



Hydrogen 6.3 ... 6.0 ... 11.37 



Oxygen 49.7 ... 47.0 ... 14.97 



I shall now refer to the three varieties of coal usually subjected 

 to distillation for their products and shall take first, bitumi- 

 nous coal, used for gas making and yielding valuable aromatic 

 hydrocarbons as a bye-product. The published analyses of 

 coals are of little value for comparison for the purpose in 

 hand, as these analyses have been made from average samples of 

 difi'erent seams to determine their commercial value, and so do not 

 take into account the fact that almost every coal is made up of a 

 mixture of heterogeneous materials varying from nearly pure 

 carbon to substances containing large percentages of hydrogen 

 and oxygen. Even in the different bands, into which coal seams 

 are divided by partings, the average of each band may differ very 

 considerably from the average of the whole. Thus in the six 

 bands of a coal seam which I recently examined, the ratio of 

 volatile hydrocarbon to fixed carbon was in each band — 



