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PRECIPITATION BY ANIMAL CHARCOAL. 
So also if we boil with acid the charcoal which has been used 
for precipitation, the precipitated oxides or basic salts contained 
therein, can almost entirely be extracted, though the last traces 
of the same resist the action of the acids. 
Mulder mentions in his Physiology , that lead can be precipi- 
tated in the metallic state from sugar of lead, by means of char- 
coal. If this were the case, no oxide of lead could be ex- 
tracted by boiling the washed charcoal in acetic acid. Whether 
easily reducible, metallic oxides, for example, oxide of silver, 
can be reduced to the metallic state by charcoal, I have not 
ascertained. 
It has lately been asserted that the precipitation of the me- 
tallic salts by charcoal depends on the calcareous salt, which 
cannot perfectly be extracted by the application of acids. If 
this were the case, by the application of a salt, whose acid 
forms a very easily soluble combination with lime, a calcareous 
salt would be found in the liquid standing over the charcoal. 
In order to determine this I dissolved ten grains of corrosive 
sublimate in two ounces of water, and shook this with ten 
scruples of charcoal. The acid liquor was filtered, deprived 
of every trace of mercury by sulphuretted hydrogen, and evap- 
orated. The last drops of the liquid certainly showed distinct 
traces of lime. The charcoal used in this experiment was then 
boiled with muriatic acid, washed, and again mixed with ten 
grains of a solution of corrosive sublimate. In both the second 
and third trials traces of a calcareous salt were found in the 
liquid. When the charcoal, which had been used in all three 
experiments, was deflagrated with nitrate of potash, and the 
saline mass dissolved in water, a very small residue only was 
obtained ; which, moreover, was only partially soluble in 
muriatic acid. It, therefore, appeared to be improbable, that 
a salt of lime should be extracted out of it by means of a solu- 
tion of corrosive sublimate, rather than by means of muriatic 
acid. And, moreover, if this even had been the case, the con- 
tained calcareous salt would have been removed after I had 
three times treated the charcoal with corrosive sublimate. The 
