_Ammonio-nitrate of Silver._--The inability of your correspondent
PHILO-PHO. to form the ammonio-nitrate of silver from a solution of nitrate
of silver, which has been used to excite albumenized paper, is in all
probability owing to the presence of a small quantity of nitrate of
ammonia, which has been imparted to the solution by the paper.
Salts of ammonia form, with those of silver, double salts, from which the
oxide of silver is not precipitated by the alkalies.
I cannot however explain how it was that the solution had lost none of its
silver, for the paper could not in such case have been rendered sensitive.