340 
Selected Articles. 
twelve ounces of distilled water, acidulated with two drachms 
of nitric acid. The apparatus being thus arranged, the bel- 
lows were set in action, by which means the atmosphere, 
loaded with the moisture from the lead, was made to pass in 
a continued current through the liquid ; this was continued for 
six hours. The whole was then transferred into a platina 
dish, and evaporated to perfect dryness. The residue was 
dissolved in one ounce of distilled water, with two drops of 
nitric acid, to insure the solution of the lead, should any be 
present. A current of sulphuretted hydrogen was next passed 
through the solution, which immediately gave a minute dark 
precipitate ; this being collected on a filter, and washed, was 
transferred to a watch-glass, and treated in the usual manner 
with nitric acid to decompose the sulphuret, which gave on 
the application of hydriodate of potash, the most unequivocal 
proof of the presence of lead. 
Another experiment was conducted at the same time with 
similar vessels, in the same room, but the current of air was 
not passed through the liquid. This, on the application of sul- 
phuretted hydrogen, gave not the least indication of lead, but, 
on evaporating the whole to dryness, and treating the residue, 
in the manner before described, with hydriodate of potash, the 
slightest possible trace of the yellow iodide of lead was per- 
ceptible. The nitric acid and distilled water were separately 
tested with great care, but were found perfectly free from 
lead, so that, no doubt, the trace of lead must have been ab- 
sorbed from the atmosphere, as the bottle containing it stood 
beside the one through which the current of air was passed. 
I ought to have mentioned before, that the temperature of the 
laboratory during the experiment was from 70° to 80° Fahr., 
and that the door was kept closely shut, that the air might be 
loaded as much as possible with the vapour. 
Lon, and Ed. Phil. Mag. and Jour. Frank. Institute. 
