ACTION OP LEAD IN DISTILLED AND RIVER WATER. 17 
water so as to deprive it of all atmospheric air, that when 
it had regained its former temperature, and was placed in a 
well-stoppered bottle with a piece of lead, the bottle being 
perfectly full, although no action was apparent, and the 
lead remained almost as bright as when first placed in the 
bottle, yet if a little hydrosulphuric acid was added to the 
water, it instinctly became of a brown color, showing the 
presence of lead, the water having on cooling absorbed 
sufficient atmospheric air to act on the lead. If, on the 
contrary, the water was placed in the bottle when warm, 
and the lead immediately added, and the bottle stoppered, 
on cooling a vacuum was formed, which it was impossible 
to maintain, and the lead was acted upon. I therefore re- 
peated the last experiment, but took the precaution, when 
the bottle was quite full and no vacuum had formed, to 
plunge the stopper under mercury, and to pour water above 
the mercury. The experiment was allowed to remain for 
some months; the lead retained its original brightness; and 
on breaking off the neck of the bottle, it being impossible 
on account of the vacuum to take out the stopper, not the 
slightest effect was produced on the liquid by hydrosul- 
phuric acid, thus proving that pure water, without the pre- 
sence of air, has no action on lead. 
" From my experiments I am led to the same conclusion 
as Colonel Yorke, as to the manner of the formation of the 
white precipitate ; in fact, I have obtained small masses of 
crystalline scales, which have formed on the surface of 
lead, which have dissolved without the slightest efferves- 
cence in acetic acid. I do not think, however, any fixed 
composition can be assigned to this substance, as on re- 
peating his experiment of drying it under the air-pump 
upon two different specimens, one of which had been kept 
some years, and the other only a few weeks, in the former 
a much larger amount of carbonic acid was found than in 
the latter, showing that the precipitate had no definite com- 
position, but that it depended, as to the quantity of carbo- 
ns* 
