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Hypophosphite measurement problem

I need to measure the concentration of sodium hypophosphite in the plating bath with the presence of Sn+2. I used to use oxidizers to measure the hypophosphite in Nickel's bath. However, since Sn+2 is also a kind of reducer, that method doesn't work for both Tin and hypophosphite. Anybody know how to eliminate Tin out of the solution and measure the concentration of hypophosphite?

Lisa Brown
- New York, New York
2003

You don't indicate what concentration levels you are trying to determine. If both the hypophoshite and tin are at say 25 to 250 g/L you may be able to use the fact that the rate of reaction of Sn(II) with iodine is very fast compared with hypophosphite. The Sn(II) may be titrated quickly and directly with iodine to a starch endpoint. Then, the total Sn(II) + hypophosphite may be found by adding an excess of iodine and titrating the excess with sodium thiosulphate ⇦this on eBay or Amazon [affil links] . Subtract the Sn(II) equivalents to find the hypophosphite concentration. Accuracy may depend upon the skills of the analyst and there are several interferrents to these procedures. I suggest that you refer to a good quantitative analysis text. Good luck!

Billie J. Page
- Cleveland, Ohio, USA
2003