M. C. Lea—Chloride, Bromide and Iodide of Silver. 353 
varies somewhat in color, is sometimes black, oftener purple 
black. If the treatment with hypochlorite has been thorough, 
strong cold nitric acid of 1:36 sp. gr. extracts from it no silver. 
This reaction with nitric acid is important as it shows that not 
only metallic silver was not present, but that the product con- 
tained absolutely no uncombined subchloride. For if any were 
present it would instantly be decomposed by the acid, in 
which one-half of its silver would dissolve. The action there- 
fore appears to take place in this way. First subchloride is 
formed, part of this is further chlorized into normal chloride 
which at once combines with other subchloride, thus taking it 
out of the further immediate action of the hypochlorite and 
this goes on until an equilibrium is reached and neither metal- 
lic silver nor uncombined subchloride is left, as is proved by 
the action of nitric acid. Alkaline hypochlorite, as will pres- 
ently be shown, attacks uncombined subchloride very rapidly, 
the combined very slowly; by many days’ contact the quantity 
of combined subchloride is gradually reduced. 
Prolonged treatment with hot strong nitric acid destroys all 
the ee of photochloride. The time needed varies a good 
deal. A specimen of that obtained with hypochlorite required 
twenty-five hours’ heating with acid of 1°36 in a water-bath at 
212° F. to bring it to the condition of white normal chloride. 
Considering that cold dilute nitric acid instantly destroys freshly 
precipitated argentous chloride in the free state, this long re- 
sistance to strong acid at the temperature of boiling water must 
be considered most remarkable. 
When the red or photochloride is formed with the aid of a 
ferrous salt or ferrous oxide, I prefer to boil the product with 
dilute HCl to get rid of the last traces of iron, after a prelimi- 
nary treatment with hot dilute nitric acid has removed silver 
and uncombined subchloride. The photochloride will some- 
times even resist boiling aqua regia for a time. 
Protected from light, as is perfectly stable, 
Specimens obtained eighteen months ago appear to be quite 
unchanged. 
When treated with ammonia, it is far more slowly attacked 
than the normal. The ammonia dissolves the normal chloride 
only. The union between the two must therefore be broken 
up and this takes place slowly. The first action of the 
ammonia is to change the red or purple color to greenish black 
and then to slowly dissolve out silver chloride. Hours are 
required even with a large excess of ammonia. Whilst this is 
going on, if the ammonia is poured off and replaced with nitric 
acid, the original color reappears. If the action is continued 
sufficiently long, silver only remains and dissolves readily in 
nitric acid. A little short of this, treatment with nitric acid 
