M. C. Lea—Chloride, Bromide and Lodide of Silver. 359 
Photochloride by Action of Potash with Oxidizable Organic Sub- 
stances. 
There is no better,method of obtaining photochloride than 
by acting on a salt of silver with potash and certain organic 
substances. Milk sugar, dextrine and aldehyde, give particu- 
larly good results. Milk sugar acts rapidly, dextrine slowly. 
Other substances with which, combined with potash, I have 
obtained chloride, are: gum, tannin, gallotannic acid, manna, 
glycerine, alcohol, carbolic acid. ete. The number might 
doubtless be indefinitely multiplied. After the action has 
reached a proper stage, which with milk sugar is apt to be in 
less than a minute and with dextrine may take half an hour, 
HCl is added, whereupon the precipitate changes in appearance 
but does not exhibit its characteristic color until after boiling 
with nitric acid; the best result is obtained when the precipi- 
tate, after addition of HCl, has a rich chestnut brown shade,* 
which by nitric acid changes to shades of purple and burnt 
carmine, when milk sugar, dextrine or aldehyde has been the 
reducing agent. When the salt of silver employed has been 
the chloride, of course treatment with HCl is superfluous. 
_A specimen obtained by acting on silver nitrate with potash 
and dextrine was found to contain 2°26 per cent of subchloride. 
Another obtained with silver nitrate, potash and milk sugar 
contained only 0°34 per cent. As in former instances these 
determinations are useful only in indicating the extreme varia- 
bility of these substances and their approximate limits of com- 
position. 
Other fieactions leading to the formation of Photochloride. 
A few more instances are here added, indicating the variety 
of ways in which this product may be obtained. 
The following is an interesting reaction. If a solution of 
ferrous sulphate is made strongly acid with HCl and solution 
of silver nitrate added, the silver is thrown down as white 
chloride. But if to the silver solution is first added a little 
ammonia, enough to re-dissolve the oxide, but much less than 
enough to neutralize the acid added to the iron solution, then 
on pouring the silver solution into the iron, the silver falls as 
red chloride. So obtained it has at first a dull purple or 
shade, but by purification, as before described, a good product 
is obtained. This method, however, scarcely tends to the pro- 
duction of the splendid copper red shades of color that are got 
by acting on silver chloride dissolved in ammonia with fer- 
* A specimen in this stage and before treatment with nitric acid was found to 
contain 92°68 per cent of silver, showing it to be a mixture of metallic silver 
with chloride and sub-chloride. 
