856 IM. C. Lea—Chloride, Bromide and Iodide of Silwer. 
Action of Various Metallic Oxides on Silver Oxide. 
If we precipitate ferrous oxide with potash and add to this 
silver oxide, or what amounts to the same thing, if we add to 
ferrous sulphate potash in excess and pour over this silver 
nitrate solution, the silver oxide separated by the potash is 
partly reduced by the ferrous oxide, and when treated with 
HCl forms red chloride, the intensity of the color of which de- 
pends within certain limits on the amount of reduction of the 
silver oxide. 
Similarly if we treat solution of manganous sulphate with 
excess of potash and then add silver solution, we getan anal- 
ogous reaction, except that it is much weaker and heat is 
necessary. 
With chromous oxide the action is still weaker, but evident. 
With cobaltous oxide it is scarcely perceptible without heat 
and long continued action. 
Action of Ferric Chloride on Metallic Silver. 
It has been long known that silver was blackened by ferric 
chloride, and this action has been proposed in the text books 
as a means of obtaining subchloride, for which it is quite un- 
suited. 
Ferric chloride acts on silver much as sodium hypochlorite 
does, but less rapidly. With hypochlorite the action is com- 
plete in a few hours or often in an hour or less; with ferric 
chloride one or two days are required before the product ceases 
to yield silver to hot dilute nitric acied. In both eases the 
action appears to be alike in this: that no subchloride is finally 
left uncombined with normal chloride. 
The product is an intensely dark purple black, when the 
action takes place in the cold. With heat continued for many 
hours, ferric chloride can be made to attack the purple salt and 
gradually convert it into AgCl. With a strong solution in 
large excess kept at or near 212° F. for sixty hours the color 
was gradually reduced to pink and finally to a dingy pinkish 
gray. Pure white cannot be obtained, as it can by aqua regia. 
In order to observe more exactly the course of the action, a 
strong solution of ferric chloride was allowed to act on reduced 
silver in fine powder for four minutes, and then a fresh portion 
(always in large excess) for the same time. Analysis showed 
that at this stage of the action the material contained: 
Ag (determined) ---- 76°07 
Cl (by difference).._. 23°98 
100°00 
