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SELECTED ARTICLES. 
small quantity of lead has not been detected, because the li- 
quors were too acid. This property of the salts of lead 
affords an easy means of separating this metal from small 
quantities of arsenic, copper, silver, antimony, or mercury, 
as these are completely precipitated in very acid solutions. 
If to the before mentioned solution (1 acetate of lead and 
200 water) we add 15 per cent, of its weight of hydrochloric 
acid, it is not precipitated by sulphuretted hydrogen, but 
when a little water is added, an abundant precipitate of sul- 
phuret of lead is immediately thrown down. 
The same solution mixed with 10 per cent of hydrochloric 
acid gives, with sulphuretted hydrogen gas, a fine red pre- 
cipitate, which retains its color, and is a sulphochloride of 
lead. 
Mixed with only 5 per cent, of hydrochloric acid, this solu- 
tion of acetate of lead gives, with sulphuretted hydrogen, a 
precipitate, at first red, but which soon becomes brown, and, 
finally, black. 
A solution, containing one part of acetate of lead in 500 
parts of water, acts in the same manner with sulphuretted 
hydrogen, as that containing one part of acetate of lead in 200 
of water, when the two solutions are acidified with the same 
quantity of acid, except that when the solution contains 
10 per cent, of acid, it is still precipitated red by sulphuretted 
hydrogen; but the red precipitate is not permanent, and with 
5 per cent, of hydrochloric acid, the solution T l^-, affords at 
once a black precipitate with sulphuretted hydrogen. 
Tin presents, under these circumstances, an interesting 
property. Since this metal is not precipitated by hydrochlo- 
ric acid, we can render the solutions much more acid than 
those of lead, and thus accomplish its thorough separation 
from other metals, such as arsenic. 
One part of prochloride of tin dissolved in 100 parts of 
water, was mixed with twenty-five of hydrochloric acid, and 
the solution treated with sulphuretted hydrogen. At first 
there was no precipitate formed; but in the course of time the 
