Chemical Experiments on GuaiacUm. 1 1 ! 



3. By being converted into a more perfect resin, in which 

 respect guaiacum bears some resemblance to the green resin 

 which constitutes the colouring matter of the leaves of trees, 

 Sec.* 



4. By yielding oxalic acid. 



5. By the quantity of charcoal and lime which are ob- 

 tained from it when subjected to destructive distillation, 



§ v. 



From the whole, therefore, of the above-mentioned pro- 

 perties, it evidently appears that guaiacum is a substance very 

 different from those which are denominated resins, and that 

 it is also different from all those which are enumerated 

 amongst the balsams, gum resins, gums, and extracts: most 

 probably it is a substance distinct in its nature from any of 

 the above, in consequence of certain peculiarities in the pro- 

 portions and chemical combination of its constituent ele- 

 mentary principles ; but as'this opinion may be thought not 

 sufficiently supported by the facts which have been adduced, 

 we may for the present be allowed to regard guaiacum as 

 composed of a resin modified by the vegetable extractive 

 principle, and as such, perhaps the definition of it by the 

 term of an extracto-res'm may be adopted without impro- 

 priety. 



P. S. I have observed that the action of oxygen on some 

 of the other resinous bodies is very remarkable. It is well 

 known, that by digesting mastich in alcohol* a partial solu- 

 tion only is formed, and there remains an elastic substance, 

 which is generally said to possess the properties of pure 

 caoutchouc: it appears, however, to differ from this sub- 

 stance, in becoming hard when dried by exposure to air. 

 Moreover, I have remarked that the part of mastich which 

 remains dissolved by alcohol, may be again precipitated by 

 water, and, on examination, I found the precipitate to pos- 



* This substance was fuund by Proust to be insoluble in water, and soluble 

 in alcob.j!. When treated with oxymuriatic acid it assumed tbe colour of a 

 withered leaf, acquiring the resinous properties i:i greater perfection. — l\dt 

 ui'» System of Chemistry, 2d edit. vol. iv. p. S1& 



Bess 



