M, Henry Rose on Resins* 369 



in the one and other are as 4 : 1, would have the following 

 composition per cent. 28-42 oxide of silver, 71-58 resin. 

 This agrees with the result of the first analysis; in the 

 others a quantity of resin was probably precipitated along 

 with the compound.''^ 



0-3575 grammes of the compound of the resin with oxide 

 of silver, from the portion which was used in the third 

 analysis, and which contained 0*2575 grm. of resin, gave, 

 when burnt with oxide of copper, 0*243 grm. of water, and 

 0-757 grm. of carbonic acid, proving the existence of 10*40 

 per cent, of hydrogen, and 80*65 per cent, of carbon. It 

 follows from this experiment, that the resin combines with 

 the oxide of silver without decomposition. 



A solution of acetate of lead in alcohol produces im- 

 mediately, in the alcohol solution of copaiva resin, a 

 copious precipitate of a compound of the resin with oxide 

 of lead. The precipitate is less crystalline than when the 

 case is oxide of silver. When dried and heated, it melts 

 like a resin. It may be analyzed, by cautiously burning it 

 in the open air, after which, a mixture of lead and oxide 

 of lead remains ; the last of which may be dissolved out 

 by dilute acetic acid. 



In two experiments, there were obtained, 



I. From 0*455 grm. of the compound 0*074 oxide of lead & 0*048 lead 



II. 0*5755 00415 0108 



Hence, its constitutents are, 



I. II. 



Oxide of lead, . . 27*63 27-42 



Resin, 72-37 72-58 



100-00 100*00 ' 



* The mean of the composition of the compound of resin and oxide of silver 

 given in the text makes the atomic weight of the resin amount to 38-5 ; but, for 

 the reasons assigned in tlie text, the true atomic weight is probably only 38. 

 Comparing this atomic weight with the composition of the resin, as determined by 

 M. Rose, it is obvious that the true constituents of the resin are, 



40 atoms carbon = 30 



32 atoms hydrogen ^ 4 



4 atoms oxygen ^^ '4 



38 = atomic weight of the 

 resin. — EniT. 



VOL. IV. 2 B 



