368 M, Henry Rose on Resins. 



down from the solution by means of water, the precipitate 

 is easily dissolved by the addition of ammonia. A solution 

 of potash in alcohol produces no change in the alcoholic 

 solution of the resin. In like manner, the alcoholic solu- 

 tion of the resin may he mixed in any proportion, with a 

 concentrated aqueous solution of potash without any pre- 

 cipitation ; but, if water be added to the solution, then the 

 combination of the resin with the potash separates from the 

 excess of potash. 



An alcoholic solution of resin is not precipitated by solu- 

 tion of nitrate of silver in alcohol. But if some ammonia 

 be added, a combination of the resin and oxide of silver 

 falls down, which is easily soluble in an excess of ammonia. 

 The solution of the resin behaves itself towards a solution 

 of oxide of silver exactly as an acid, which forms with it 

 a difficult soluble or insoluble compound, but soluble in 

 free acid, and in free ammonia. The precipitate is crystal- 

 line, and retains its shape after drying. It is not absolutely 

 insoluble in alcohol, though it is very slightly soluble in 

 that liquid. By the action of light it is blackened like 

 the other salts of silver. At a moderate heat, it melts like 

 a resin ; at a higher, it is decomposed, and leaves after the 

 combustion of the cinder metallic silver. 



In three experiments, I obtained from quantities, which 

 were prepared at different times, by combustion, the follow- 

 ing quantities of silver. 



I. 0*308 grammes of the compound gave 0*081 grms. silver 



II. 0*321 0*082 

 111.0*376 0096 



Hence, the composition per cent, was as follows : 



I. II. III. 



Oxide of silver, . . 28*25 27*41 27-40 

 Resin, 71*75 72*59 72*60 



100*00 100*00 100*00 ^ 

 If the resin combines, without decomposition, with the 

 oxide of silver, tl;pn it contains in this compound four 

 times as much oxygen as the oxide of silver, for, in the 

 above table, the mean proportion of oxygen contained by 

 the oxide of silver is 1*9, and by the resin 7*5. A com- 

 pound of the resin and oxide of silver, in which the oxygen 



