Hydrargotype

The principle is to form iron tetracyanomercurate by releasing the ferrous ion from iron oxalate under UV light. This is also an experimental process that needs improvement, particularly with regard to the yellow oxalate haze. I have not found any reference to this process in the literature, so I have named it: Hydrargotype and filed a Soleau envelope (Stéphane Corbé - 2026).