M» Henry Rose on Resins. 367 



crystalline state, and he at first believed that it was a com- 

 bination of copaiva with ammonia,* but he afterwards 

 found that the ammonia was only formed during the pro- 

 cess, and that crystallization from alcohol alone was required 

 to obtain the resin in a state of purity .f The crystals 

 are combinations of two oblique 4-sides vertical prisms. 



Parallel to one of the faces, there are traces of cleavage, 

 which, however, are difficult to detect from the extreme 

 softness of the crystals. These are pure white, the smaller 

 transparent, the larger translucent, or only so, at the 

 edges ; they are all very soft. 



This crystalline resin is more soluble in strong boiling 

 alcohol than in cold. The spirituous solution reddens 

 litmus paper. This resin combines with inorganic bases, 

 and the compounds which it forms have all the properties 

 of salts. 



0*509 grammes of crystallized resin were put into Leibig's 

 apparatus with oxide of copper. They yielded 0*464 grms. 

 of water and 1*459 of carbonic acid. Hence, their com- 

 position is the following : 



Carbon, ..... 79*26 

 Hydrogen, . . . . 10*15 

 Oxygen, 10*59 



This composition agrees with that which Blanchet and 

 Sell have found for common resin, which, according to 

 them contains 79*65 carbon, 10*08 hydrogen, and 1027 

 oxygen. Colophonium is an oxide of oil of turpentine. 

 Now, since the composition of this last agrees, according to 

 Blanchet, with that of volatile oil of copaiva, we must also 

 consider resin of copaiva as an oxide of this oil. We see 

 also, that isomeric bodies, when oxidized, yield isomeric 

 oxides. 



The composition of copaiva resin as well as that of colo- 

 phonium may be expressed by the formula, 10 C + 16 H + O ;.}: 

 calculating from this, its constituents would stand thus, 

 carbon 79*275, hydrogen 10*355, oxygen 10*37. 



If we mix a solution of copaiva resin in alcohol with 

 ammonia, there appears, as is usual with all solutions of 

 the acid resins, no precipitate. If the resin be thrown 



* Pogg. Ann., xvii. 487. t lb., xxi. 172. 



t Rose considers the atom of hydrogen one-sixteenth of that of oxyg«n. — Edit. 



