370 M. Henry Rose on Resins. 



In this compound, also, there are four times as much 

 oxygen in the acid as in the base. A compound of copaiva 

 resin and oxide of lead, in which the proportions of oxygen 

 are as 4 : 1, would be composed of 26-56 oxide of lead, and 

 73-44 resin. 



The quantity of resin, in the portions of the compound 

 which were examined, is rather less than it ought to be 

 from this calculation, because a small quantity of carbonate 

 of lead easily falls down from the alcoholic solution of the 

 acetate, unless atmospheric air be entirely excluded. 



The alcoholic solution of copaiva resin gives no precipitate 

 with a solution of chloride of calcium in alcohol. But, if 

 the solution be diluted with water, a white precipitate 

 separates, which cannot consist of pure resin, because it is 

 insoluble in alcohol. The lime which this precipitate con- 

 tains can be separated by long continued washing. But a 

 more permanent compound of this resin and lime can be 

 obtained by adding ammonia to a mixture of the alcoholic 

 solution of copaiva resin with an excess of the alcoholic 

 solution of chloride of calcium, and allowing to precipitate, 

 which appears to fall down in a corked vessel, so as to pre- 

 vent its being mixed with carbonate of lime. It must 

 afterwards be filtered in such a manner as to prevent the 

 access of air, and washed with water as long as it does not 

 act upon lime. 



0*4195 grms. of this precipitate were cautiously ignited; 

 the residue, when treated in the usual way, with a solution 

 of carbonate of ammonia, weighed 0-0§2 grammes, and was 

 carbonate of lime. 



Hence, the compound of the resin with lime contains 

 per cent. 



Lime, .... 8-32 

 Resin, .... 91-68 



100-00 



This compound agrees with the former analogy, the 

 oxygen in the base is one fourth of that in the resin. Such 

 a compound of copaiva resin and lime would contain per 

 cent. 8-45 lime, and 91-55 copaiva resin. 



Now, since the three described and examined combina- 

 tions of copaiva resin with oxide of silver, oxide of lead, 



