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topic 34601

EN Solution analysis

A discussion started in 2005 but continuing through 2018


Q. Dear sir

I am looking for method of Ni & reducing agent determination in Electroless Ni-P.

Thank you

Roorki Univ. - Roorki, India


A. Assuming your reducer is sodium hypophosphite (you forgot to say) you will sample 5 mL from bath, use glass stoppered flask, add 5 mL concentrated sulphuric acid, add 50 mL 0.1N iodine solution, mix and place in dark for 30 minutes, add approximately 10 mL starch solution and titrate with 0.1N sodium thiosulphate (Na2S2O3) from almost black (very dark blue) to colorless endpoint.

Calculate your hypophosphite
(NaH2PO2.H2O) = (50mL (Iodine volume) x 0.1 (Normality of iodine) - mL consumed of titrant x 0.1 (Normality titrant)) x 1.413.
This will be in oz /gal x 7.82 gives g/L.

Guillermo Marrufo
Monterrey, NL, Mexico


A. I Agree with the above hypophosphite analysis as for the Nickel analysis:

10 ml sample of ENP solution at room temperature
add 10 mls of ammonia buffer (water,conc ammonia,ammonium sulphate)
100 mls water
Use murexide as an indicator and titrate with EDTA from a light brown to pink/purple end point.

Chris Matthews
- East Sussex, England

September 30, 2016

A. I would substitute the conc. Sulphuric Acid for 50% strength or lesss and add a bit more to compensate (say 15 - 20ml). You're only adding the acid to liberate excess Iodine, which then reacts with the Sodium Thiosulphate (hence the name back titration). Adding conc. Sulphuric Acid to such a small amount of sample, then pouring Iodine on top of this is a recipe for disaster, and could cause a nasty accident

Stuart Tween
- Chelmsford, Essex, UK

April 23, 2018

Q. Hello everyone. I found a thermometric redox titration with potassium permanganate as a method for hypophosphite determination.
Anyone ever used this method?
Is the endpoint a change in the temperature? In that case, is special equipment necessary to read the endpoint or can I also read it with a thermometer?

Rubén Basurto
- Cuautla, Morelos, México.

December 30, 2018

A. 1. Yes, the endpoint is determined by the change in temperature of the solution.

thermometric titration
2. Yes, thermometric titrations do need special equipment for the most accurate, precise results. Automated thermometric titration systems employ the second derivative of the digitally smoothed temperature curve. You can find more information about the subject under the search item "thermometric titration" in Wikipedia. I think more competitors would increase the profile and utility of this valuable technique.

3. Yes, I have performed many thousands of thermometric titrations, including acid/base (aqueous and non-aqueous), redox, precipitation and complexometric approaches. It is fundamentally a superior technique to potentiometric titrimetry.

Thomas Smith
Antom Technologies Pty Ltd - Bowral, New South Wales, Australia

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