If you get only 100 rings from a gram of rhodium, you’re doing
something quite wrong. Your salesman’s figure sounds about right. I’d
guess you’re some how contaminating your bath so it gets discarded
while it still has lots of rhodium in it, but due to whatever
contamination you’ve got, you no longer are getting good results. How
long are you leaving a piece in the bath to plate? Are you plating
directly over silver without under plating it first? Etc etc. When
you find a bath giving bad results, you can try to salvage it.
Filter through a coffee filter with some aquarium type activated
This won’t fix all contaminants, but will rescue the bath in some
cases. One other thing to watch is avoid getting organic solvents or
soluable organic compounds in there. In practice this means that if
you are using something to mask off parts of a ring you don’t want
to plate, be very sure your stop off material is fully dry before
plating. Also one other thing to watch is that the ph of the bath is
important. Get some ph test strips to check acid content/levels.
Sometimes all the bath needs is to add a little more sulphuric acid.
But you need to get the parameters for your bath from the
manufacturer, as they are not all the same for all of them.