Dear Dave An acquaintance has shown me a quantity (apparently several
ounces) of silver “powder”, apparently recovered from some photographic
processing operation several years back. Has anyone ever dealt with
this stuff before?
1 - Can I just melt it down in a crucible and pour an ingot? Any
idea of the purity?
Depends on the method, expertise, and carefullness of the recoverer.
2 - Any residual chemicals or toxic elements I need to be aware of?
See the answer to Question 1
3- Something best sent to legitimate refiner?