296 M. Karsten's Observations on Coal 



The loss of weight indicated by this table, whatever differ- 

 ences it may present, does not appear to have any relation to the 

 properties of the varieties of coal, and in general of the mat- 

 ters subjected to experiment. The greatest loss was experienced 

 by the fossil wood and by the coal with conglutinated coke hav- 

 ing but a small proportion of charcoal. The former substance 

 losses 19.8, and the latter 6 per cent. The more the quantity 

 of charcoal increases, the smaller does the loss of weight be- 

 come. M. Karsten, however, was surprised to see that a coal 

 analogous to anthracite, and anthracite itself, experienced a con- 

 siderable loss (from 5 to 6 per cent.), which would not have 

 been presumed from their hardness and semimetallic lustre. 



In general, the lightness, that is to say the porous and 

 loose state of a body, does not appear to have any influence 

 upon this loss of weight, or at least it does not always exert an 

 influence upon it ; for if it did so, mineral charcoal, which, 

 of all the substances submitted to trial, is the lightest and loos- 

 est, perhaps, without excepting even wood charcoal, would have 

 experienced the greatest loss. The charcoal of mineral wood, 

 however, does not lose more than 1, while the hard and shining 

 anthracite of Rhode Island loses upwards of 5 per cent. On 

 the other hand, graphite, rendered very loose by bruising and 

 pulverization, preserves its weight unaltered. Are the loss of 

 weight which charcoals experience, and their subsequent in- 

 crease on exposure to the atmosphere, owing to the emission 

 and absorption of atmospheric air and humidity, or of humidi- 

 ty only ? The author has not entered upon this inquiry ; but 

 he thinks, that, with the view of ekicidating the cause of the dif- 

 ferences which are observed in the manner in which mineral 

 combustibles comport themselves, it would be interesting to try 

 them thus at the moment of their being taken from the mine, 

 and particularly those which in the open air increase consider- 

 ably in weight. With regard to such coals as experience a very 

 considerable diminution of weight, on being dried at the tem- 

 perature of boiling water, their produce in coke by carboniza- 

 tion ought to be very small, and not to agree with the results of 

 chemical analysis, if, as is commonly done, coals dried in the 

 air be employed in the carbonization, and in the chemical ana- 

 lysis, coals dried at the temperature of boiling water. 

 (To be contimied.) 



