Answer / carl_ellis

Let's assume base metal elements only, since noble metal
elements are so expensive that they are under lock and key;
adequate protection from loss of identification.

For types T, J and K, (and by exclusion, E) the options are

-a spectropscopic assay which will positively reveal the
alloys' composition, but given that the cost of an assay is
proabably 20x times the value of a base metal element, it's
not likely to happen.

- visual identification of a type T by the copper color of
its positive leg which is copper. The alloy leg is a shiny
'metallic' color.

- testing Types J or K with a magnet.
The Type J positive leg is made of iron which has a very
strong magnetic attraction.
The Type K negative leg is made of a nickel alloy which is
mildly magnetic.
Type E is non magnetic, but so are other types.
It can be tricky to distinguish mild attraction on thin
gauge wire.

Testing with a multimeter can be very misleading, because of
the difficulty in determining both the hot junction AND the
cold junction temperatures. Without accurate temperature
values, of what use is a mV reading?

Carl Ellis
Measure First

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