Ea^periments on the different kinds of Coal. ^8S 



tlie proportion of azote is so small, in all the varieties of l)rowa 

 coal and black coal that have been submitted to examination by 

 Mr Karsten, that this substance does not appear to be an essen- 

 tial constituent part of them. 



Several brown coals and black coals yield an acid liquor by 

 distillation; but most kindsof black coal furnish none. Peat, in the 

 dry distillation, furnishes so great a quantity of acid water, that it 

 is difficult to recognise clearly in that substance the ammoniacal 

 basis which occurs in it, and this even on saturating the acid 

 with potash. 



Mr Karsten has carefully investigated and described the very 

 different effects which are produced, whether on wood, and, in 

 general, on unaltered vegetable fibre, or on altered vegetable fi- 

 bres, on peat, brown coal, and black coal, by the different che- 

 mical re-agents, such as water, alcohol, sulphuric ether, caustic 

 ammonia, hydrosulphuret of ammonia, nitric acid, and concen- 

 trated sulphuric acid. In his work we even find detailed ac- 

 counts of the processes followed in these investigations. We 

 shall confine ourselves, however, to the principal results. Those 

 which are obtained on making the acids act upon vegetable fi- 

 bres, whether altered or recent, are perfectly in accordance with 

 the manner in which acids comport themselves, and the circum- 

 stances of the body upon which they act. Nitric acid, which is 

 easily decomposed, and, from this very circumstance, capable of 

 oxidising, produces more promptly, and in a higher degree, the 

 oxidation of vegetable fibres. This acid changes them into a 

 substance analogous to tannin, or even into an acid, while sul- 

 phuric acid can only operate a conversion of the fibres into gum, 

 and finally into sugar. Unaltered fibre undergoes its metamor- 

 phoses more quickly and more completely, because the greater 

 proportion of the quantity of oxygen and hydrogen to the quan- 

 tity of carbon facilitates the action of acids. 



In proportion as the quantity pf carbon increases, the chemi- 

 cal effect of acids becomes more and more feeble, and perfectly 

 pure charcoal appears no longer susceptible of alteration from 

 acids, excepting in a single case, which happens when this sub- 

 stance occurs, as it does in wood-charcoal, in a loose state of 

 mechanical aggregation. 



Glance coal, graphite and diamond resist the action of acids ; 



