So with iridium and rhodium, and osmium and
ruthenium, which are so closely allied that they make pairs, being
separated each from its own group. Then these metals are the most
infusible that we possess. Osmium is the most difficult to fuse: indeed, I
believe it never has been fused, while every other metal has. Ruthenium
comes next, iridium next, rhodium next, platinum next (so that it ranks
here as a pretty fusible metal, and yet we have been long accustomed to
speak of the infusibility of platinum), and next comes palladium, which is
the most fusible metal of the whole. It is a curious thing to see this
fine association of physical properties coming out in metals which are
grouped together somehow or other in nature, but, no doubt, by causes
which are related to analogous properties in their situation on the
surface of the earth, for it is in alluvial soils that these things are
found.
Now, with regard to this substance, let me tell you briefly how we get it.
The process used to be this. The ore which I shewed you just now was
taken, and digested in nitro-muriatic acid of a certain strength, and
partly converted into a solution, with the leaving behind of certain
bodies that I have upon the table. The platinum being dissolved with care
in acids, to the solution the muriate of ammonia was added, as I am about
to add it here.
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