which possesses the characteristic Properties of Tannin . 133 
The coal obtained by the humid process from many of the 
resins, was shining, hard, and occasionally iridescent. Few 
of the coals obtained from the same bodies by fire had any of 
these properties. The combustion of the former was slow in 
the manner of some of the mineral coals, whilst on the con- 
trary the latter were speedily consumed like charcoal. This 
difference I was at first inclined to attribute to a small portion 
of the acid which might not have been completely separated, 
and I therefore purposely made some experiments which 
convinced me that this was not the case. 
Having remarked this difference in the coals afforded by 
the resins, I was desirous to make some comparative experi- 
ments on wood, and for this purpose I selected oak. 
1. 
On 480 grains of oak sawdust I poured two ounces of sul- 
phuric acid diluted with six ounces of water, and placed the 
matrass on a sand-bath, where it remained from the begin- 
ning of last June to the end of September. During this time, 
the sand-bath had very seldom been heated, but the vessel 
was occasionally shaken. 
At the end of the period above mentioned, six ounces of 
boiling water were added, and the whole being poured upon 
a filter, was repeatedly washed, and was afterwards dried on 
a sand-bath in a heat not much exceeding 300°. 
The sawdust appeared to be reduced to a granulated coal, 
partly pulverulent, and partly clotted ; the whole weighed 
210 grains. 
105 grains of this coal were put into a platina crucible, and 
were exposed to a red heat under a muffle. At the same 
