324 ARSENIC IN PAPER-HANGINGS. 
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of which the w r alls were covered with paper-hanging, ex- 
hibiting a large pattern of a light green colour. The surface 
of the paper was not glazed, and the coloured portions were 
found to have on their surface about two tenths of a grain 
of arsenic per square inch. In the first experiment the room 
was kept thoroughly closed for about thirty-six hours: a 
portion of its atmospheric contents were then drawn, by an 
aspirator, first through a solution of nitrate of silver, and 
then through a tube containing asbestos moistened with 
ammonio-nitrate of silver. In the sepond experiment, air 
was passed through these tests for a longer period than in the 
first (about five hours), and three gas-lights had previously 
been kept burning in the well-closed room for several hours. 
Not a trace of arsenic was detected by a Careful examination 
of the tests at the close of these experiments. 
3d Experiment. — A large glass tube (3 feet 3 inches in 
length, and % inches in diameter) was next filled with slips of 
arsenical papef-hanging, placed in a small room, in a posi- 
tion where it could be raised to a temperature of about 
90° F., and connected with a similar apparatus to that em- 
ployed in the former experiments, containing solutions of 
nitrate and ammoniornitrate of silver. Air was then drawn 
through the apparatus uninterruptedly for one week (by 
means of a Johnson's Aspirator ), three gas-lights being kept 
burning in the closed room, at intervals, for several hours. 
The air passed through the apparatus at the rate of one cubic 
foot in two hours, 
4 th Experiment,— Air was passed through the apparatus, 
as before, for twenty-four hours; the tube containing the 
paper was kept warm, and the air was made to pass 
through a strong sblution of sulphurous acid before it reached 
the tube. v 
6th Experiment, — The end of the tube at which the air 
entered was connected with a large funnel suspended imme- 
diately over a burning gas-jet ; hot air, mingled with the 
products of the combustion of gas, was thus made to pass 
over the paper for three days. 
6th Experiment,- — The fifth experiment was repeated, the 
air being passed uninterruptedly for four days. 
7 th Experiment, — Hot air was passed through the tube, as 
in the fifth and sixth experiments, for nine days, the coloured 
surface of the arsenical paper having first been thoroughly 
roughened by friction, so as to promote the mechanical de- 
tachment of the arsenical pigment by the current of air, and to 
favour to the greatest extent the possible volatilization of 
arsenic. It should be mentioned, that in all these experi- 
