Summary for hypophosphorous acid titration Discussion
Hypophosphorous acid in tin plating bath: Gtong asked how to measure hypophosphorous acid at about 50-120 g/L when Sn+2 is also present at 25-70 g/L, and whether tin could be removed first. No direct separation method was offered in the thread. Instead, Terry Tomt suggested a simpler approach: try an acid-base titration to estimate the hypophosphorous acid directly, which would avoid the tin interference. He noted that he had no direct experience with the acid, but pointed out that hypophosphorous acid is classified as a powerful reducing agent. The discussion therefore leans toward analytical titration as a practical workaround rather than chemical removal of tin.
2006
I need to measure the concentration of hypophosphorous acid in the plating bath with the presence of Sn+2. Anybody know how to eliminate Tin out of the solution and measure the concentration of hypophosphorous acid?
The concentration of hypophosphorous acid is about 50-120g/L and the tin concentration is about 25-70g/L.
Thanks,
Gtong
student – Hong Kong
A. I would filter the sample carefully, then do a titration with either standard iodine or iodate solution. This gives you the combined Sn2+ and hypophosphite concentration.
Then, I would determine the tin concentration via AA spectroscopy ⇨
and get the hypo result by difference. If I did not have an AA, I would assay the tin by a gravimetric method using cupferron as precipitant, followed by ignition of the precipitate, and weighing the resultant SnO2.
Dave Wichern
Consultant – The Bronx, New York
Gtong –
Maybe this is a dumb idea, but could you get an idea of the hypophosphorous acid simply by doing an acid-base titration? Then you wouldn’t need to eliminate the Sn+2 interference. I don’t have any experience with this acid, but I see that is is classified as a powerful reducing agent.
Terry Tomt
– Auburn, Washington