366 M, Henry JRose on Resins. 



following, 5th, the oil of the balsam of copaiva ; 6th and 7th, 

 the two oils which compose the oil of juniper, extracted 

 from unripe fruit;* according toEttlingt 8th, oil of cloves, 

 and 9th oil of valerian have also the same composition, 

 when they are separated from the acids with which they 

 are combined. 



The most of these are certainly not mixtures of several 

 substances, for they have been united with muriatic acid so 

 as to form crystalline compounds, some of which have been 

 often examined. The compounds which they form with 

 oxygen have been much less frequently examined than they 

 deserve, since they belong in part to the most common 

 kinds of resins. 



Blanchet and Sell have examined colophonium, and 

 found that it might be considered as an oxide of oil of 

 turpentine. But when the experiments of Unverdorben 

 and of Ries determined colophonium to be composed of two 

 resins, one of which could be obtained in crystals, they 

 considered that substance as a mixture of isomeric resins. 



Besides that which exists in colophonium, several other 

 crystalline resins have been detected, and their investigation 

 is peculiarly interesting, as they are pure compounds, and 

 are not formed of a mixture of several different substances. 



Now, as resins appear usually to be formed by the oxida- 

 tion of volatile oils, it appeared to me to be important to 

 ascertain the relation in composition which exists between 

 the resins obtained from isomeric oils. This investigation 

 can be carried farther than that of the oils themselves, 

 because the most of the resins formed from oils, as Unver- 

 dorben has long ago shown, behave as acids, and are capable 

 of forming saline compounds with inorganic bases. I have 

 examined a few crystalline resins of both these kinds, and 

 though they might undoubtedly have been increased, I 

 have here communicated my results. 



RESINS WHICH HAVE THE PROPERTIES OF ACIDS. 



Resin from Balsam of Copaiva. 



No resin can be obtained in such beautiful crystals as 

 this. Schweitzer first gave a method of obtaining it in the 



* Ann. der Pharmacie, vii. 154. Pogg. Ann. xxxi. 526. 

 t Ann. der Pharmacie, ix. 68. Pogg. Ann., xxxi. 526. 



