172 FREER. 



exudation of the resin, although Mr. Richmond, in subsequent careful 

 investigations of the trees, concluded that such must be the case. 



The study of amorphous bodies, such as resins, which in by far the 

 greater part yield only amorphous decomposition products, is naturally 

 attended with great difficulty, and consequently the publication of the 

 results from this laboratory has been delayed for a long time. The 

 work was begun by Dr.- Penoyer L. Sherman, and continued by Mr. 

 George P. Richmond and Mr. Benjamin T. Brooks, the botanical work 

 being by Dr. F. W. Poxworthy. 



Manila copal is for the greater part composed of amorphous resin 

 acids, with but a small proportion of a neutral, amorphous solid, which 

 is left behind on exhaustive treatment with alkalies. It is this latter 

 body which darkens rapidly on melting and which, in all probability, 

 is the cause of the deepening of the color of the resin when it is heated 

 for varnish making. The pure resin acids, on heating, do not darken 

 very much. Manila copal also contains a certain, but small percentage, 

 of terpenes. It is interesting to note that, whereas Manila copal, per 

 se, rapidly oxidizes on exposure to the air, the pure acids, as isolated by 

 Mr. Richmond, could be redissolved, precipitated, and even distilled with- 

 out apparent change, the oxidation phenomena appearing to take place in 

 the original resin. 



Copal gives off carbon dioxide even at ordinary temperatures if it is 

 exposed to the air, and more rapidly in the sunlight. Undoubtedly 

 this phenomenon is due to the formation of peroxides, and whereas it 

 may be of importance in the finely powdered substance, it can not be 

 of such great moment in the alterations which take place in the solid 

 pieces, as otherwise the latter would have suffered profound changes and 

 would, according to the length of their exposure to air, differ markedly 

 in their composition and properties, a fact which does not appear from 

 the work which has been carried on in this laboratory. It is well known 

 that the resin hardens promptly when it exudes from the tree, but this 

 effect has nothing to do with oxidation. The small percentage of carbon 

 dioxide which passes off at lower temperatures when copal is heated also 

 shows that no profound oxidation has taken place. 



The resin acids are therefore present in the exudate as it issues from 

 the tree. The analyses which at present exist give no proof that these 

 acids are closely related to each other, neither has anything been done 

 which can clear up their constitution. The one crystalline acid, C 10 H 15 0.,, 

 forms only a small proportion of the whole, and although conjectures as 

 to its nature are obvious, much more work needs to be done upon it. 



The studies which follow show some advances on the present methods 

 of producing oleoresinous varnishes by outlining the means by which 

 they may be prepared at lower temperatures, and they show the way by 

 which the local trade could be supplied with satisfactory varnishes made 

 entirely from Philippine materials. 



