Perhaps this may help someone to answer my question.
Below is what I have.
Production of Rainbow Hues on Brass
The sulphide of tin may be deposited on metallic surfaces , espically on brass, communicating shades varying with the thickness of the deposit. For this purpose, Puscher prepares the following solutions:
Disolve tartaric acid 20 parts, water 1000 parts.
add, a salt of tin, 20 parts, water 125 parts.
Boil the mixture, allow it to repose and filter.
Afterwards pour the clear portion a little at a time, shaking continually, into a solution of…
hypossulphite of soda 80 parts, water 250 parts.
On boiling sulphide of tin is formed, with precipitation of sulphur .
On plunging the pieces of brass in the liquid, they are covered according to the period of immersion with varied shades, passing from gold yellow to red, to crimson, to blue, and finally to light brown
Salt of tin must be one of the following.
Tin chloride (stannous), SnCl2
Tin chloride (stannic) SnCl4
Tin oxide (stannous), SnO
Tin oxide(stannic) SnO2
Can someonr tell me which one, please.