610
LEAD—SACCHARUM SATURNI.
Here the acid is found to have greater effect when applied in the
form of vapour. A certain quantity unites with the lead, in the
form of a white powder, which is afterwards much more easily dif
folved. This fubstance, diffolved in distilled vinegar, affords salt of
lead, called saccharum faturni, from the ſweetiſh tafte with which it
affects the tongue, resembling that of fugar. It crystallizes, or rather
grains, very readily. If the salt be again diffolved in more vinegar,
it combines with a greater proportion of it, becomes more soluble, and
affords fine crystals.
With the tartarous acid, lead forms a compound very insoluble. It
may be produced by boiling a folution of tartar, and adding any pure
oxyd of lead. The superfluous acid of the tartar joins with the lead,
as with chalk, and forms an insoluble sediment ; and the tartar is thus
neutralized, being deprived of the acidulating part of its acid.
Or if, instead of an oxyd of lead, we take a compound of this
metal with nitric or acetous acid, and add this compound to a solution
of tartar, or any liquor which contains tartar diffolved in it, the tar
tar is then completely decompounded by a double elective attraction ;
the whole of its acid uniting with the lead, to form a white insoluble
precipitate.
Lead also forms an insoluble compound, in the fame manner, with
the acid of phosphorus, which can therefore be precipitated from
urine by a folution of lead.
When we, in the next place, compare the forces of attraction be
tween lead and these different acids, we find the strongest is that of
the sulphuric acid. Other metals in general unite most strongly with
muriatic acid ; but in the case of lead, it is the sulphuric acid that is
moft strongly attracted, and when combined with the lead, it always
forms an insoluble compound. It therefore precipitates lead from
other acids, by joining itself to this metal in their place. This hap
pens, not only with pure ſulphuric acid, but with any falt or ſaline
compound which contains the fulphuric acid. In however small