BED LEAD 281temperature, stirring frequently, and finally boil it for 30 min-
utes, replacing water lost by evaporation. Transfer the con-
tents of the dish to a 2-liter common bottle and wash the
sludge by decantation with cold water (see Note 5 (6), page
10) until over 99 per cent of the soluble chloride is removed.
Then transfer the sludge again to the dish, add 250 cc. of &N
HN0 3 , and boil it for 10 minutes. Wash the residue of lead
dioxide by decantation until the wash water is no longer acid;
transfer the product to a filter and let it drain without suction
(Note 4 (c), page 7). After the lead dioxide has drained, remove
the filter and contents carefully from the funnel, unfold the filter,
and spread it on paper towels on the steam table to dry. When
completely dry, detach the lumps of lead dioxide from the paper,
and pulverize them in a mortar. Put up the product in a 2-ounce
cork-stoppered bottle.QUESTIONS- Why could not lead dioxide be prepared equally well by
treating a solution of lead chloride with chlorine? - Compare the reaction of lead dioxide and of lead monoxide
with hydrochloric acid. - Compare the action of lead dioxide with that of manganese
dioxide upon hydrochloric acid. - Why should not lead dioxide and manganese dioxide dissolve
in dilute nitric acid as well as in hydrochloric acid?
PREPARATION 48
RED LEAD, Pb 3 O4
Of the oxides of lead, the monoxide PbO is the most stable when
heated to a high temperature, and in fact all the other oxides
are converted into this one when they are heated strongly in con-
tact with the air. At a moderate heat, however, the monoxide
is capable of taking on more oxygen from the air until the com-
position approximates that of the formula Pb 3 O4. This substance
is not to be regarded as a simple oxide of lead, but rather as a
compound of PbO and PbO 2 , in which the monoxide is the basic
component and the dioxide the acidic. It may thus be regarded
as the salt, lead orthoplumbate, 2PbO-PbO 2 = Pb 2 (Pb0 4 ). This