PAPERS OX CHEMISTRY AND PHYSICS 131 



A STUDY OF THE EFFECT OF METALS IX 



CONTACT WITH SOLUTIONS OF SILVER 



HALIDES IX VARIOUS SOLVENTS 



J. H. Baksom and D. W. Haxsox, James Milliklx 



UxiVERSITY 

 PRELEUIXARY PAPER 



During the performance of an experiment by a class 

 students large quantities of a very dilute solution of 

 silvei - - were produced, from which, both for eco- 

 nomic reasons and for its effect on the student, it was 

 desired to recover the silver. It occurred to one of the 

 authors that the easiest and most direct way to recover 

 the silver was to convert it into chloride, dissolve this 

 in some solvent like ammonia, and precipitate the silver 

 by treatment with some metal like iron or zinc. Whether 

 metals would preci] silver from such solutions was 



not known ai . arch through the available literature 



did not indicate that the experiment had ever been tried. 



When silver chloride is dissolved in ammonia it is be- 

 lieved that a complex positive ion results which contains 

 both silver and ammonia, AgiXII > : . Since more than 

 the equivalent amount of ammonia is necessary to pro- 

 duce solution it is probable that this positive ion is in 

 equilibrium with the silver ion. the concentration of the 

 latter ion decreasing with the increase in concentration 

 of free ammonia. In any such solution, however, there 

 might be enough silver i that in contact with 



metals whose solution tension was greater than that of 

 silver ions the latter might be discharged and the silver 

 deposited. A preliminary trial with such a solution 

 gave a gray powder appearing somewhat metallic. 



The solutions of silver salts, left over from the stud- 

 experiment, were collected and the silver precipi- 

 tated by an excess of hydrochloric acid. After washing 

 the silver chloride it was dis in rather concen- 



d ammonia, making a nearly saturated solution. 

 To this was add zinc. Almost immediately 



the gray deposit formed, together with some gas, prob- 

 ably hydrogen, and towards the end of the experiment 



