the charaderhtic Properties of Tannin. 65 



The sulphuric acid almost immediately dissolved the resins, 

 and formed transparent brown solutions, which progres- 

 sively became black. 



The same effect was produced on most of the other sub- 

 stances, but the solutions of the balsams and of guaiacum 

 were at first of a deep crimson, slightly Inclining to brown. 



Caoutchouc and clastic bitumen were not dissolved, but, 

 after having been digested for more than two months, were 

 only superficially carbonized. 



The gums and the saccl»arine substances required many 

 evaporations and filtrations before the whole of their car- 

 bonaceous residua could be obtained. 



These were the principal effects observed during the ex- 

 periments, and I have stated them in this manner, that 

 tedious and useless repetitions may be avoided.- 



§ n. 



Turpentine, common resin, elemi, tacamahac, mastich, 

 copaiba, copal, camphor, benzoin, balsam of Tolu, balsam 

 of Peru, asa fcetida, and amber, yielded an abundance of 

 the tanning substance. 



Oil of turpentine also afforded much of it; asphaltum 

 yielded a small portion ; some slight traces of it were even 

 obtained from gum arable and tragacanth ; but none was 

 produced by guaiacum, dragon's blood, myrrh, gum ammo- 

 niac, olibanum, gamboge, caoutchouc, elastic bitumen, 

 liquorice, and manna. I am persuaded, however, that many 

 of these would have afforded the tanning substance had not 

 the digestion been of too long a duration. 



Olive oil was partly converted into the above-mentioned 

 •substance, and also linseed oil, wax, and animal fat; but 

 the three last appear to merit some attention. 



IJmeed Oil. 



This oil with sulphuric acid very soon formed a thick 

 blackish-brown liquid, which, after being long digested in A 

 sand-bath, was still partly soluble in cold water, and passed 

 the filter. This solution precipitated gelatine ; the residuum 

 was a tough black substance, which became hard on expo- 

 sure to air. A great part was soluble in alcohol, and formed 



Vol. e7. No. lo."). Ffh. 1907. E a brown 



