I don’t have an answer for you. However, they are all using the same
basic method to remove the copper and silver - an acid.
bisulphate is a very weak acid
nitric is a very strong acid.
The strength of the acid determines the rate. so dilute nitric at
the same pH will dissolve e. g. copper at (approximately) the same
rate as the equivalent pH bisulphate.
However, some acids will or will not dissolve different metal, and
this is determined by the salt that forms, its solubility and the
nature of the species that coat the surface of the metal.
simple version, if the metal and acid form a soluble salt (with
exceptions) it will dissolve the metal.
I know nitric will work on silver and copper but not gold. it is
safer when dilute, so the trick isn’t to avoid conc nitric it’s to
use dilute nitric in everyday work, and only handle nitric when
making up a fresh solution.
can you buy already diluted nitric?
always add acid to water to dilute - not water to acid. Think of it
this way. All the energy is in the acid. you only want to add a
little energy at a time. when you add water to acid, all the energy
available local to the water causes it to boil and spit…
Nitric has a love affair with carbon and starch. ruined a few pairs
of jeans leaning against a spill on a bench un-noticed. it will turn
wood brown. which is still better than turning melamine brown…
several explosives are made by using nitric acid to nitrate