When present in sufficient quantity the five last-named give enamel-white beads; lead oxide in excess gives a yellowish bead.
Tin is removed mainly as a powdery mixture of stannate of lead and lead oxide, arsenic and antimony as a slagged mixture of arsenate and antimonate of lead and lead oxide.
It is also obtained by passing chlorine into a suspension of lead oxide or carbonate, or of magnesia and lead sulphate, in water; or by treating the sesquioxide or red oxide with nitric acid.
The invention, if it may be regarded as one, consisted in eliminating lime from the glass mixture, substituting refined potash for soda, and using a very large proportion of lead oxide.
Sometimes reagents are placed in the combustion tube, for example lead oxide (litharge), which takes up bromine and sulphur.
