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Author: Subject: monobasic and dibasic of sodium phosphate
jamit
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[*] posted on 3-1-2018 at 21:53
monobasic and dibasic of sodium phosphate


so i've checked around google search and I'm kind of confused and wonder if someone can explain or help me sort this out. I have sodium phosphate monobasic and dibasic. The only difference between the two is the number of sodium and number of water ligands. they are both reagent ACS chemical purity but the monobasic is now all clumped up because it probably absorbed water. Has it become dibasic? How can I tell?

Why would anyone want just the monobasic as opposed to dibasic? I realize that sodium phosphate is used in analytical chemistry to make buffer solutions. Does it make a difference whether you use monobasic or dibasic?

And how can I convert monobasic to dibasic and vice versa? It is just a matter of heating it and weighing it to find out which is which?

And is the anhydrous formed if it is heated strongly? Any thoughts on this will be appreciated. thanks.

[Edited on 4-1-2018 by jamit]

[Edited on 4-1-2018 by jamit]

[Edited on 4-1-2018 by jamit]
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violet sin
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[*] posted on 3-1-2018 at 22:15


https://en.m.wikipedia.org/wiki/Sodium_phosphates
Non, mono, do and tri basic sodium phosphate.

H3PO4, NaH2PO4, Na2HPO4, Na3PO4 = how many times has a base ran off with a proton, from full acid to all full of Na.




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jamit
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[*] posted on 3-1-2018 at 22:58


thanks but I already knew that link.

Do you know why chemical supplier sells the various hydrates of sodium phosphate? Why not just sell the anhydrous of both monobasic or dibasic sodium phosphate.

the hydrate of sodium phosphate just makes stoichiometric calculation more difficult in that over time, the monohydrate turns into dihydrate and heptahydrate and so on.

I have NaH2PO4 H2O but I am afraid that clumping of the chemical indicates that it has picked up water. So do I have dihydrate now or what? Can I just put it into a desiccator and dry it and will it then go back to being a monohydrate or will it turn into anhydrous?
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[*] posted on 4-1-2018 at 04:30


Quote: Originally posted by jamit  
Why not just sell the anhydrous of both monobasic or dibasic sodium phosphate.


Because that would usually involve them spending money to roast the material to drive off water- that's particularly pointless if the next thing that happens is you make a solution of it.
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nezza
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[*] posted on 4-1-2018 at 07:41


Phosphoric is a tribasic acid and forms 3 sodium salts as has been explained earlier. Th pKa of the "acid" phosphates are different and the two salts are often used to make buffer solutions around pH 7. Each salt forms a different hydrate, which obviously has to be taken into account when making up known concentration salts.



If you're not part of the solution, you're part of the precipitate.
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