ON FUEL ECONOMY. 288 



(3) a portion, insoluble in ether, consisting of non-resinous material, partially 

 dissolved by alcoholic potash, and this they designate as ' humic substance.' 

 The authors are satisfied that these humic substances are not ' resinic ' but 

 ' cellulosic ' in origin. The influence of these several fractions on the coking 

 of a coal has been studied, with the result that, whereas the said resin is in 

 part responsible, the main cause of the coking propensities was shown to be a 

 series of substances of ' humic ' type which are soluble in chloroform but not 

 in ether, and whose fusion temperatures are below those at which they undergo 

 rapid decomposition. 



The acidic substances extracted by alkalis from the aforesaid humic bodies 

 are precipitated by acids from these solutions, as bulky, dark-coloured, opaque 

 jellies. These jellies on drying form black, brittle, lustrous, and structureless 

 masses, with conchoidal fractures, suggestive of the material forming bright 

 coal which Stopes has styled ' vitrain.' The consideration of these facts has 

 led Bone and his co-workers to suggest that ' bright coal ' may have originated 

 in a colloidal gel. 



In this connection attention may be directed to a like conclusion arrived at 

 by Dr. J. A. Smythe in 1906, in a paper read before the University of Durham 

 Philosophical Society^ which dealt with certain Peaty Deposits from a Pit-Fall 

 at Tantobie, County of Durham. Amongst the substances described is a black 

 jelly-like body, which Smythe styled ' black-stuff,' and this he showed by its 

 composition and behaviour to solvents, notably to pyridine, suggests a similar 

 relationship to bright coal. 



It has long been recognised that bituminous coals contain three easily 

 distinguishable components, which until recently had usually been designated 

 (a) 'mother of coal' or 'mineral charcoal,' (h) 'dull hard coal' (Ger. = 

 ' Mattkohle '), and (c) 'bright coal' (Ger. = ' Glanzkohle '), respectively, the 

 last named being a structureless, lustrous substance with a conchoidal fracture. 

 Recently Stopes {Proc. Roy. Soc, B. 90 (1919), p. 470) proposed new names 

 for them, namely {a) fnxm'n, (b) durain, whilst (c) Is termed by her either 

 clarain or vitrain, according as it does or does not contain recognisable plant 

 tissues and structures. In putting forward these proposals Stopes recognised 

 that none of the four said ingredients (with the possible exception of vitrain) 

 are either homogeneous or chemical molecular units ; also that they do not even 

 approximately represent the crystals in a petrological section of a rock. Pro- 

 vided that such qualifications are kept clearly in mind, and that it be realised 

 that clarain may prove to be merely vitrain in which plant structures occur in 

 suspension, the Committee sees no great objection to the provisional substitution 

 of the proposed new names for the older ones, regarding the matter more 

 as one of convenience than 'as involving any new principle. 



The Committee also feels that the growing practice among coal-chemists 

 to use the terms alpha, beta, (jamma, &c., to designate the severnl components 

 obtainable from the coal substance by fractional extraction of it by means 

 of various solvents, is one which, unless regularised in some definite way, is 

 likely to lead to much confusion and obscurity, to the detriment of progress. 

 It is obvious that coal may be ' fractionated ' in as many different ways as 

 there are suitable solvents and modes of applying them ; and therefore unless, 

 as the results of some particular treatment or procedure, components of a 

 reasonable decree of purity and well-defined properties are isolated, it is 

 undesirable that definite names should be assigned to them, as though they 

 were the actual chemical constituents of the coal instead of unknown mixtures 

 of them. The Committee, therefore, would suggest that the time has come 

 when chemists should aeree in conference upon some common plan of labelling 

 such 'coal fractions' which, whilst recognising them to be such, shall also in 

 some way indicate how they have been obtained. 



Supposing, for example, that a particular investigator extracts a coal with 

 two solvents A and B, he misrbt desio-nate the fraction which is insoluble in 

 both as the a AB fraction, whilst (i AB might be used to denote the fraction 

 which is soluble in A but not in B, and the 7 AB that which is soluble in 

 both A and B, assuming all solvents to be used at their respective boiling 



3 University of Durham Philosophical Society Procrcdivgf, Vol. 2, pt. fi. 



