354 M. C. Lea— Chloride, Bromide and Iodide of Silver. 
leaves a black residue of dark chloride mixed with metallic 
silver; the dark chloride being insoluble in any acid has led 
to some strange mistakes in a similar reaction which occurs in 
treating with ammonia silver chloride that has been exposed to 
the light. Even a theory has been had recourse to of a “ pas- 
sive condition” of silver. This passive silver is simply black 
chloride. 
A specimen of purple black chloride was treated with warm 
strong aqua regia until whitened by conversion of the sub- 
chloride to normal. By this treatment 2563 grams of photo- 
chloride gained nine milligrams, indicating the presence of 24 
per cent of subchloride, or more exactly 
Subchlorider eee er a se ee ee Oe) 
Normalichilorides2 2522s. ee. bp ek unl ron 97°51 
This is not to be taken in any sense as representing a con- 
stant composition. The proportion of subchloride varies be- 
tween certain limits, not only according to the method of prep- 
aration used but independently of it. Another specimen of 
black chloride formed with hypochlorite gave figures that 
indicated a content of less than half of one per cent of sub- 
chloride. 
Photochloride by Keduction of Normal Chloride. 
This is an excellent means of obtaining red chloride. The 
white chloride is to be dissolved in ammonia and ferrous sul- 
phate added, producing an intensely black precipitate. After 
standing a minute, the mixture is to be treated with dilute sul- 
pburic acid until it shows a strong acid yeaction. 
The precipitate is to be first well washed by decantation, 
then boiled first with dilute nitric, then after washing with 
dilute hydrochloric acid, which must of course be thoroughly 
washed out. 
The product obtained in this way is often of singular beauty. 
It might easily be taken for metallic copper. Sometimes it is 
as rich and bright in color as the copper obtained by electric 
deposition. Everyone knows the richness and brilliancy of 
that form of copper and I have seen it fully equalled by this 
silver salt. 
The beauty of the color depends always on the thorough re- 
moval of any metallic silver that may be present, and still more 
on getting rid of every trace of iron. ‘The boiling with dilute 
hydrochloric acid should be continued until, after thorough 
washing, a fresh treatment extracts no more and the acid re- 
mains colorless in presence of alkaline sulphocyanide. 
Instead of an ammoniacal solution of silver chloride, we may 
