360 M. 0. Lea—Chloride, Bromide and Iodide of Silver. 
rous sulphate and then adding dilute sulphuric acid. The 
shade of color shown by any particular specimen is always of 
interest, because as before mentioned, it modifies the effect 
exerted upon it by the spectrum. 
Potassio-ferrous oxalate-—The now well-known “ oxalate de- 
veloper” which I described in this Journal some years ago, 
throws down from silver nitrate a black powder; this precipi- 
tate treated with HCl scarcely alters in appearance, but washed 
and boiled with dilute nitric acid, changes to a deep purple. 
Pyrogallol is capable of leading to the formation of photo- 
chloride. When ammoniacal solution of silver nitrate is 
poured into solution of pyrogallol in water made strongly acid 
with HCl, in such proportion that the mixed solutions remain 
strongly acid, there falls a grayish product which by washing 
and treatment with hot dilute nitric acid, becomes bright pink. 
Ferrous oxide differs essentially in its action on silver solu- 
tions from ferrous sulphate. A silver nitrate solution added 
to one of ferrous sulphate, precipitates gray metallic silver. 
But if potash or soda is first added to the ferrous solution 
and then silver nitrate followed by HCl, the red chloride is 
formed abundantly. This reaction is similar to that already 
described in which an ammoniacal solution of a silver is added 
to one of ferrous sulphate. 
To the same class of reactions belongs the following: silver 
carbonate with excess of sodium carbonate is thrown into solu- 
tion of ferric sulphate, and after standing a few minutes HCl 
in excess is added. The silver is converted into red chloride. 
It seemed possible that silver itself might be made the means 
of reducing its chloride. The experiment was made in this 
way: freshly precipitated and still moist chloride was inti- 
mately mixed with metallic silver in fine powder and a little 
water. ‘This was heated till the water boiled and nitric acid 
was added. After the action was over the chloride had 
assumed a deep pink color. A similar result is obtained with- 
out the aid of heat, but the resulting color is much paler. 
Analogous to this is the following: When a cake of fused 
silver chloride in a crucible is reduced with dilute sulphuric 
acid and zine, if the reduction is interrupted when not quite 
finished, and the metallic silver is dissolved out with hot nitric 
acid, the residue of silver chloride will be found to be pink. 
When HCl is brought into contact with Ag together with an 
oxidizing agent such as a bichromate or permanganate, it gives - 
rise to formation of colored chloride. These I have not spe- 
cially examined, but there can be little doubt that they are 
identical in nature with the foregoing. So too when silver in 
contact with mixed potassium chloride and chlorate is cau- 
tiously treated with dilute sulphuric acid. 
