Bulk phase and chemical composition analysis of two 19th century Russian platinum coins by neutron and complementary methods

The composition of early 19th century platinum coins reflects the advances of platinum metallurgy from laboratory-scale refining to industrial-scale processing. An array of neutron methods was used to determine for the first time the bulk phase and elemental composition of two coins, dated 1837 and 1838. Neutron imaging confirmed the homogenous internal structure of the metal at the micrometer scale, with further support from small-angle neutron scattering at the nanometre scale. Prompt gamma activation analysis showed the coins to consist of technically pure platinum, appropriate for the time of their production with iridium and iron between 1 and 2 weight percent. Lower amounts of copper, rhodium, manganese and gold were also detected in the range of tens to thousands of g/g. Overall, the investigation demonstrated the suitability of neutron methods as noninvasive and reliable bulk means to determine the composition of early industrial platinum to track the development of refining processes and metallurgical processing.