This, then, will give you an idea of what has to be done by any
process that pretends to deal with thirty, or forty, or fifty pounds of
platinum at once.
Let me now tell you briefly what Deville proposes to do. First of all, he
takes this ore, with its impurities, and mixes it (as he finds it
essential and best) with its own weight of sulphuret of lead--lead
combined with sulphur. Both the lead and the sulphur are wanted; for the
iron that is there present, as you see by the table, is one of the most
annoying substances in the treatment that you can imagine, because it is
not volatile; and while the iron remains adhering to the platinum, the
platinum will not flow readily. It cannot be sent away by a high
temperature--sent into the atmosphere so as to leave the platinum behind.
Well, then, a hundred parts of ore and a hundred parts of sulphuret of
lead, with about fifty parts of metallic lead, being all mingled together
in a crucible, the sulphur of the sulphuret takes the iron, the copper,
and some of the other metals and impurities, and combines with them to
form a slag; and as it goes on boiling and oxidising, it carries off the
iron, and so a great cleansing takes place.
Now, you ought to know that these metals, such as platinum, iridium, and
palladium, have a strong affinity for such metals as lead and tin, and
upon this a great deal depends.
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