§g ^ TANNING MATTF.n, ScC. 



_ . One luind red trains of the same masticli ojily gave 4^ 



Experiments, *=• . ^ . . , , , "^ ^ 



&c. on an arti- grains of coal when simply distilled. 



ficlal substance And 100 grains of amber, when, treated with sulphuric 



racteJf of^ tani ^^id, yielded 56 grains of coal.' 



ning matter. But from 100 grains of the same amber when distilled, 



onlj 3{ grains could be obtained. 



Many other examples might be adduced, but these ap- 

 pear to be sufficient ; aiid 1 must here observe, that the 

 case is very diiferent-in respect to the gums, for the dif- 

 ference between the proportions of coal obtained from 

 them by the humid and dry ways is not very consider- 

 able, although it is always the greatest in the former 

 process, when conducted with precaution. Moreover it 

 is to be remarked, that in either process, variations in 

 ' the quantity of coal are produced by difference of tem- 



' perature, by the figure and size of the vessels, and many 

 other circumstances. 



But it is not only in the proportion, that there is so 

 great a difference between the coal obtained from the re* 

 sinous substances by the humid way or by fire, for the 

 quality is also most commonly different; and this not 

 only applies to the resins but also to ligneous matter. 



The coal obtained by the humid process from many of 

 the resins, was shining, hard, ant^ occasionally iridescent. 

 Few of the coals obtained from the same bodies by fire 

 had any of these properties. The combustion of the for- 

 mer was slow in the manner of some of the mineral coals, 

 whilst on the contrary 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 pur- 

 posely 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 

 experiments on wood^ and for |^is purpose I selected 

 oak. 

 - ~ L 



On 480 grados of oak sawdust I poured two ounces of 

 (iiulphuric acid diluted with six ounces of water, and 

 placed the jnatras* on a sand-bath, where it remained 



from 



