Of the furnace must be so% greater than that of the kettle into which the softened lead is tapped, as the dross and skimmings formed amount to about so% of the weight of the lead charged.
Browne finds that after smoking " chandoo," containing 8.98% of morphine, 7.63% was left in the dross, so that only 1.35% of morphia was carried over in the smoke or decomposed by the heat.
The last distinctive epithet was derived from the little hamlet in the vicinity which furnished shelter, not only to the workmen, but to the monks of St Jerome who were afterwards to be in possession of the monastery; and the hamlet itself is generally but perhaps erroneously supposed to be indebted for its name to the scoriae or dross of certain old iron mines.
The lead is melted down slowly, when the impurities separate in the form of a scum (dross), which is easily removed.
For smoking the Chinese use an extract of opium known as prepared opium or chandoo, and a cheaper preparation is made from 60% used opium known as " opium dross " and 40% native opium.
For this end, disrepute and poverty are advantageous, in so far as they drive back the man upon himself, increasing his self-control and purifying his intellect from the dross of the external.
A redistilled zinc, from an ordinarily pure commercial zinc, is often called chemically pure, but redistillation is seldom practised except for the recovery of zinc from galvanizer's dross and from the skimmings and bottoms of the melting furnaces of zinc rolling mills.
A bath, even of very impure zinc, is allowed to stand at about the temperature of the melting-point of the metal for forty-eight or more hours, whereupon the more easily oxidizable impurities can be largely removed in the dross at the top, the heavier metals such as lead and iron settling towards the bottom.
" The Chinese recognize the following grades of opium: (I) ' raw opium,' as imported from India; (2) ' prepared opium,' opium made as above; (3) ' opium dross,' the scrapings from the opium pipe; this is reboiled and manufactured as a second-class prepared opium; a Chinese doctor stated lately at a coroner's inquest on a case of poisoning that it was more poisonous than the ordinary prepared opium; (4) ' nai chai ' (opium dirt), the insoluble residue left on exhausting the raw opium thoroughly with water.
The laborer, looking into it at evening, purifies his thoughts of the dross and earthiness which they have accumulated during the day.