The best way to do this is to have a dedicated distilled water rinse
for EACH solution. Keep this rinse water, do not dispose of it, have
a dedicated beaker and a seal for all the rinse waters. Treat these
rinse waters as if they were solutions. Then as the solution starts
to dissipate or lose strength add the rinse water back into the
And congratulations, most people contaminate their rhodium solution
before depleting it.
Rio Grande Technical Support