Mateo_swe
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KHSO4 Potassium bisulfate
I have been looking for some Potassium bisulfate KHSO4 but even though its used in winemaking it seem very hard to buy anywhere at a decent price.
I found one seller that had a good price on it on ebay but unfortunately it does not deliver to my country.
So, can i make it then?
I looked into this and apparently its a byproduct when making nitric acid HNO3 from sulfuric acid H2SO4 and potassium nitrate KNO3.
The procedure seem quite easy too, mix equal weights of KNO3 and H2SO4 in a reaction flask and distill over the formed nitric acid
at 83-84°C to a cooled receiver flask.
The KHSO4 is remaining in the reaction flask.
KNO3 + H2SO4 -> KHSO4 + HNO3
Thats an option as both sulfuric acid and potassium nitrate is cheap.
I dont really know what i going to do with the nitric acid but maybe it can be useful sometime in the future.
The nitric acid apparently should be briefly degassed under vacuum to remove excess dissolved nitrogen oxides.
KHSO4 is also made in the first stage in the Mannheim Process when making potassium sulfate.
KCl + H2SO4 -> KHSO4 + HCl First stage
KCl + KHSO4 -> K2SO4 + HCl Second stage
The second stage reaction need high temperature so it should be easy to stop at the first stage.
I think i prefer the nitric acid method, i have the sulfuric and P nitrate already.
So unless i find some cheap KHSO4 for sale somewhere i will be making some KHSO4 by the nitric acid method.
Its unfortunate its not NaHSO4 as this is sold cheap in pool supplys.
Whats the KHSO4 for?
I want experiment with making puruvic acid and for that i need KHSO4.
I know i can buy puruvic acid and i already have some, but i want experiment with making it myself.
Anyone know a cheap source of KHSO4 or have some comments on the nitric acid method to make KHSO4?
Is there a better/simpler/safer way to make KHSO4?
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Oxy
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Another option is bromic acid synthesis from potassium bromide and sulfuric acid.
Regarding safety of method which produces nitric acid - it is safe however nitric acid, especially concentrated, is something that should be handled
with care. And during the synthesis you may need to remove significant amount of NOX if you will overheat. Some nitrogen oxide will be produced anyway
so do it in fume hood, outside or use some efficient washing system.
Of course you may not want to store >95% HNO3 as it's kind of problematic but you may add some water to reaction flask and distill azeotropic HNO3.
You will definitely find many uses for nitric acid as it strong and oxidizing acid. Can be very handy in inorganic and organic preparations.
I am not sure if I KHSO4 is sold as pH regulating agent for swimming pools, I was looking on pool supplies in hardware store few weeks ago.
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unionised
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As far as I know, it isn't used in wine making.
The bisulphite is.
Boiling sulphuric /nitric acid isn't a nice material to work with.
You can buy potassium carbonate- which really is used in wine making- and react that with an excess of sulphuric acid and crystallise out the product.
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Mateo_swe
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Thanks for all advice and ideas.
I already have potassium carbonate and sulfuric acid, so that certainly is an option.
I must look up the procedure, what more is generated and how to isolate the KHSO4.
Then i dont have to deal with the hot HNO3, and i already have a bottle of HNO3 so i really dont need any more at this time.
Wikipedia said KHSO4 was used in winemaking, maybe its not, i dont make wine.
In the OrgSyn Pyruvic acid preparation KHSO4 and tartaric acid are reacted forming pyruvic acid.
I wonder if NaHSO4 could be used instead of the KHSO4.
I have a lot of NaHSO4, it might be worth trying before i make any KHSO4.
The OrgSyn procedure says a variety of dehydrating agents were tried and they settled on KHSO4.
So NaHSO4 might work, maybe with a bit lower yield.
It would be an interesting experiment, i think i must test if it works.
OrgSyn Pyruvic acid preparation:
http://www.orgsyn.org/demo.aspx?prep=CV1P0475
Edit:
What do they mean when they write "freshly fused potassium acid sulfate"?
That it was recently made or heated to drive out any small % water before use?
[Edited on 2021-9-7 by Mateo_swe]
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Texium
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Quote: Originally posted by Mateo_swe  | I already have potassium carbonate and sulfuric acid, so that certainly is an option.
I must look up the procedure, what more is generated and how to isolate the KHSO4. |
Quite simple...
You just dissolve the potassium carbonate in water. Add two molar equivalents of sulfuric acid (slowly, because it will release lots of carbon
dioxide), and evaporate to yield crystals of potassium bisulfate.
Really, there's nothing wrong with the nitric acid method either. Yes, it's more dangerous, but nitric acid is a valuable product (more valuable than
the bisulfate), and it's a procedure that's been used by countless amateur chemists. I've done it a few times, and I would typically just throw out
the leftover potassium bisulfate slurry! You can easily recrystallize the residue from water though, to remove excess traces of nitrate and acids that
may remain.
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macckone
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those of us that make nitric acid, it is a bi-product.
For anyone else, I would suggest the potassium carbonate, sulfuric acid route.
Another method not discussed is simply bubbling air through the bisulfite solution.
It is readily oxidized to the bisulfate but it is slow and you probably want it dry.
For those that are impatient add 3% hydrogen peroxide then boil off the water.
Potassium sulfate is also available as a fertilizer, that can also be converted to bisulfate by addition of sulfuric acid.
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Fantasma4500
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i know NaHSO4 is sold in hardware stores as pH minus, combines easily with the respective hydroxide to produce sulfate
but it seems you have settled with going for the potassium variant.
anyhow if you really desire KHSO4,* you can buy "caroat" pool oxidizer, i believe thats what its called, its a mix of KHSO5, KHSO4 and K2SO4
its a moderate oxidizer, dissolves metals somewhat and pyrotechnically a low end oxidizer
if youre gonna make it with acid, why not just go for KOH? carbonate sucks, only excuse to react acid with a carbonate if you can just buy the
hydroxide instead would be to use the CO2 for growing plants
[Edited on 14-10-2021 by Antiswat]
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