ON THE PROXIMATE CHEMICAL CONSTITUENTS OF COAL. 247 



For the purposes of a preliminary study a coal representing the Hutton 

 seam in the county of Durham was selected. This coal is a bituminous 

 coal, and is used as a gas coal. When heated with ether it yields up to 

 the solvent a small amount of a substance which imparts a light yellow 

 colour to the ether, and a blue fluorescence is observed, similar to that 

 noted by Dondorff in his experiments with a gas coal of the Westphalia 

 Coalfield. Alcohol, benzene, and petroleum ether dissolve but little from 

 the coal, the solutions being in each case similar to that obtained with 

 ether. 



Acetic anhydride and glacial acetic acid were employed as solvents 

 with but little eflfect. Somewhat more promising at first were the results 

 obtained by using a solution of sulphur dioxide in glacial acetic acid. 

 The coal was heated at 100° C. with this solution in tightly closed 

 flasks. The liquid becomes dark in colour, and on adding water to the 

 solution a light yellow precipitate is formed. The precipitate is dissolved 

 by ether, and the ethereal solution on evaporation leaves an oily residue, 

 which was found to be partially volatile in steam. 



Turpentine heated at 150° C. in a tightly closed flask with the 

 powdered coal dissolves some constituent, becoming darker in colour and 

 acquiring a greenish-blue fluorescence. 



When the coal is heated with aniline a brown amorphous solid is 

 dissolved out, which is precipitated from the aniline on acidifying with 

 Hydrochloric acid. This substance is not unlike that obtained by Guignet 

 by treatment of coal with phenol. It was attempted to separate this 

 solid into several fractions by treatment with alcohol and benzene. 

 The alcoholic and benzene solutions, however, left merely resinous sub- 

 stances on evaporation. Dilute solutions of potassium permanganate 

 oxidise this solid, forming dark brown solutions containing potassium 

 carbonate and the potassium salts of organic acids. The quantity of 

 material being small, it was next decided to treat the coal itself with 

 potassium jjermanganate. For this purpose finely powdered coal is sus- 

 pended in water, to which, when boiling, potassium permanganate is added 

 in small quantities at a time. The colour of the permanganate gradually 

 disappears, and an odour resembling that of turpentine is observed ; at the 

 same time a dark brown alkaline liquid is formed. 



The amount of permanganate which is thus reduced by the coal is 

 considerable : in one case where 500 grams of coal were taken, some 1,600 

 grams of permanganate were employed without exhausting the reducing 

 power of the coal, of which some 25 to 30 per cent, had been oxidised in 

 this manner. 



The aqueous solution decanted off from the manganese dioxide and 

 coal is very dark in colour, becoming almost black when concentrated. 



Amongst the acids formed in this way, oxalic acid has been found, 

 together with some deliquescent acids, which on the evaporation of their 

 aqueous solutions are left as brown resinous masses. The separation of 

 these products is still incomplete, and it would be futile to give the results 

 of the analyses of the salts which have been prepared. The barium salts 

 appear to afford a means of separating the acids, some of which salts have 

 been already obtained in a fairly pure condition. The account of these 

 acids and the study of the action of potassium permanganate on other 

 coals it is proposed to deal with in a subsequent report. 



