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How can I reduce the saccharin in the nickel sulfamate bath?

I have a big electroforming tank (1700 liters) of nickel sulfamate(Ni-speed process) to make holographic shims and I have a lot of problems to control the saccharin level. I had a concentration of 1,45 g/l and I wanted only 0,1 g/l. I filtered the bath with active carbon during three weeks and it didn't work. After this I spent more than 50.000 A.H.T. doing shims because I had heard that the saccharin level would reduce if I worked a lot with the bath, but the saccharin level is the same. Obviously I didn't add more saccharin. What do you thing about this? Is it possible to reduce the level? And, what can I do?

Thanks,

Jesus Guell
- Barcelona, Spain
2002

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Saccharin cannot be removed. Carbon does not remove saccharin. Drag-out or cut and add back are the only ways. If your analysis is HPLC you may be reading some other sulfur compounds in addition to the "saccharin". Organic sulfur contamination of cheap granular activated carbon is very common and it is frequently added in with the saccharin by the HPLC. It is very difficult to find "sulfur free" activated carbon. Run a Hull Cell panel before and after adding your carbon, and if the bright low is moved leftward or up the current density scale - then your carbon is loaded with sulfur.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2002

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While saccharin doesn't absorb much at normal pH as it is in salt form, I think it would do better at low pH Try in lab sample lowering pH with sulfamic acid ⇦this on eBay or Amazon [affil links] and then doing carbon treatment to see if this helps. Also try analysing by a different means to ensure you do have this much saccharin. Did that much actually go in?

Geoffrey Whitelaw
- Port Melbourne, Australia
2002