Four metals found in a residue

01

The part that would not dissolve

Crude platinum from South American deposits was treated with a mixture of acids that dissolves the metal. What remained was a dark insoluble powder, easy to treat as impurity. Two collaborators divided the problem: one worked on what dissolved, the other on what did not. The decision to treat the residue as a sample rather than as waste is the whole method of the episode, and it produced four elements from material that had been thrown away.

DOE — Platinum

02

Separating chemically similar metals

The platinum-group metals share the noble character that makes platinum useful: they resist attack by most reagents and by air. That resistance is also what makes separating them difficult, because the reactions available to distinguish them are few. The analysts worked by precipitating fractions with different reagents and examining the color, form and behavior of what came down, building the case for a new element from an accumulation of properties rather than from a single test.

LANL Periodic Table — Platinum

03

Why they occur together

These metals sit adjacent in two rows of the table and share a chemical character, so geological processes that concentrate one tend to concentrate the group. Modern refining still recovers them together and separates them afterwards, often as a by-product of nickel and copper production. The economics follow from the chemistry: an element that never occurs alone is priced by the whole process that produces it.

RSC Periodic Table — Platinum

What followed

The platinum group is still recovered and separated as a set, and its members are used where resistance to attack matters most: catalysis, electrical contacts, laboratory ware and spark plug electrodes.

DOE — PlatinumLANL Periodic Table — PlatinumRSC Periodic Table — PlatinumDOE — PlatinumLANL Periodic Table — Platinum