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Topic: Hypo-phosphite vs hypo-phosphate  (Read 1527 times)

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Offline pcm81

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Hypo-phosphite vs hypo-phosphate
« on: June 06, 2018, 07:39:31 PM »
One on my current projects is electroless nickel deposition. I have several electro-less nickel plating bath recipes all of which are calling for sodium hypophosphate (3x Oxygens) as a reducing agent.
I have sodium hypo-phosphite (2 oxygens) which I have used before in EN bath. The way this reaction works is that sodium phosphite (or hypo-phosphate) absorbs an oxygen from water releasing 2 protons, which then reduce nikel ion to metallic nickel. Bath runs at pH between 4 and 6.

My question is this: Since I have Na+H2PO2 rather than Na+H2PO3, do i need to simply use 1/2 of the quantity listed in recipe?

Side question:
Some of my sodium hypophosphite feels a bit wet. Probably absorbed some moisture from the air. Is it safe to heat it up to say 130 degrees F to dry it? Is there a better way?

Thanks

Offline pcm81

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Re: Hypo-phosphite vs hypo-phosphate
« Reply #1 on: June 06, 2018, 07:56:29 PM »
One on my current projects is electroless nickel deposition. I have several electro-less nickel plating bath recipes all of which are calling for sodium hypophosphate (3x Oxygens) as a reducing agent.
I have sodium hypo-phosphite (2 oxygens) which I have used before in EN bath. The way this reaction works is that sodium phosphite (or hypo-phosphate) absorbs an oxygen from water releasing 2 protons, which then reduce nikel ion to metallic nickel. Bath runs at pH between 4 and 6.

My question is this: Since I have Na+H2PO2 rather than Na+H2PO3, do i need to simply use 1/2 of the quantity listed in recipe?

Side question:
Some of my sodium hypophosphite feels a bit wet. Probably absorbed some moisture from the air. Is it safe to heat it up to say 130 degrees F to dry it? Is there a better way?

Thanks

I also have access to a vacuum chamber and could try to de-hydrate the sodium phosphite in that, if that is the preferred way or at all makes sense.

Offline Arkcon

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Re: Hypo-phosphite vs hypo-phosphate
« Reply #2 on: June 08, 2018, 07:48:27 AM »
The difference between phosphite and phosphate is an oxidation state.  They are likely not interchangeable, although I haven't checked you math.  You could certainly try it, on a small scale, to see the difference.

Your water reaction with sodium salts to produce protons isn't a real one that I expect to happen.  If you found it in a text book you should share the reference with us.

I have no idea what the vacuum chamber is supposed to do in this context.

You seem new to basic chemistry.  I'm sorry if my answers aren't more helpful, but we're clad to fill in a few concepts.   But everyone here, on the forums, new student, professional who needs a refresher, engineer who has lost touch with the basics or even the home chemist with a brilliant new idea is called upon, by all of us, to cover the basics on their own.  That's part of the Forum Rules{click}.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline pcm81

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Re: Hypo-phosphite vs hypo-phosphate
« Reply #3 on: June 08, 2018, 08:24:48 PM »
The difference between phosphite and phosphate is an oxidation state.  They are likely not interchangeable, although I haven't checked you math.  You could certainly try it, on a small scale, to see the difference.

Your water reaction with sodium salts to produce protons isn't a real one that I expect to happen.  If you found it in a text book you should share the reference with us.

I have no idea what the vacuum chamber is supposed to do in this context.

You seem new to basic chemistry.  I'm sorry if my answers aren't more helpful, but we're clad to fill in a few concepts.   But everyone here, on the forums, new student, professional who needs a refresher, engineer who has lost touch with the basics or even the home chemist with a brilliant new idea is called upon, by all of us, to cover the basics on their own.  That's part of the Forum Rules{click}.

The description of the reaction is found on page 213 of this book: https://metalfinishing.epubxp.com/t/12238-metal-finishing-guide-book
The chemical reducing agent most commonly used is sodium hypophosphite
(NaH 2 PO 2 ); others include sodium borohydride (NaBH 4 ), or an aminoborane
such as n-dimethylamine borane (DMAB) [(CH 3 ) 2 NHBH 3 ]. Typical reactions
for a hypophosphite reduced bath are as follows:
H2PO 2— + H 2 O H + + HPO 32— + 2H
Ni 2+ + 2H Ni + 2H +
H 2 PO 2— + H H 2 O + OH — + P

In this text they do mention H2PO2 as the reducing agent, but other recepies use H2PO3, so i was curios if i can use h2po2 for both recepies by adjusting the concentration.

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