Russian Chemistry Abbreviation?

[K M Harkness]

I'm translating an article about ancient bronzes found in Siberia.  In an extensive chart listing the chemical composition of the objects, the abbreviation Н. о [N. o] appears in two places in the iridium column.  I cannot for the life of me figure out what this means and it isn't in the list of abbreviations.  (The authors use a — when an element is absent and Сл. [Sl.] when a trace is present.)  Help please!

Many thanks in advance.

Kristen Harkness

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