Extracting H3PO3 from phosphite foliar solutions

[halfkast]

I'd bee fairly confident what you have there has largely gone through this process largely undegraded. So you can still retreive it in good yields.

All that has happened is that the first evaporation you did failed to evaporate enough water to start putting pressure on that KCl to fuck off out of the water - to precipitate.

This is good on one hand, because we know the phosphorous acid has been nice and safe from oxygen because it's in a diluted solution.

1. evaporate off as much of that alcohol and water as you can, using a evaporating dish your comfortable with pouring liquid out of carefully.
(Keeping in mind that the more you evap the better for KCl removal)

2. mix a glass off 50ml of alcohol and 100ml of HCl and add it to the evaporation dish solution, which you've just partially evaporated in order to concentrate it.

3. Mix it gently but thoroughly. Leave it sit there for 10-20min.

4. Pour the solution in to another evaporation dish, leaving the KCl behind.

5. evaporate this final evaporation dish to relative drying using a fan and a/c.

Room temperature fan and air conditioner/de-humidifier is better than the fan forced oven and all that heat.

[dalewilj]

Thank you for your response. Good to know that swim has partial dream. Question, It seems that getting rid of H20 as hypo is very hydroscopic. Would it be unresonalble to make izzy (goldberg) contraption i.e (buckner filter with some dehydrating materal (damp rid, KMNO4,etc) plus small negative air pressure to evaporate. Seeing as swim haas no dehumidifer and it's 20 degrees out side to run a/c.
   One other question. Swim left supernatant in freezer in ice maker with the ice. Now swim has abot 60 grams of a white slurry of xtals in flask. With about 150 ML of fluid. The temp of fluid is about 5 degrees F. Should swim dump the fluid and keep xtals or just dump in  dish and evaporate all xtals and solution.

[halfkast]

The temp of fluid is about 5 degrees F. Should swim dump the fluid and keep xtals or just dump in  dish and evaporate all xtals and solution.

No keep it all, don't throw any liquid away throughout the entire procedure in fact, remembering that every solvent used in the procedure dissolves the desired end product.

much of the crystal formations your seeing are in all likelyhood KCl precipitating out because of the low temperatures, and generally the quantitative and qualitative properties of the constituents (solvent and solutes).

the liquid is the unfrozen methylated spirits.

Evaporate off as much of the liquid you can and then think about how your going to cause the H3PO3 to dissolve leaving the KCl behind. (eg. using alcohol that has been acidified with HCl)

I have no idea about this goldberg apparatus. I mean if you have faith in it use it, but just remember H3PO3 solutions can clog filters pretty quick.
Not potassium permanganate...


Really though, if you find it doesn't really work well for you, know that the a/c and fan work well, and I strongly suspect it's of much higher quality than the origional fan-forced oven variety.  

[Un_Chambered]

Would there be a reason why 99% ipa wouldn't work as the alchol in this procedure?
Swic is kinda strapped for cash and has lots of the above and none of anything else.My guess would bee yes and thats what swic'll go with barring a more definitive answer.
Thanks and peace,Chambered

[halfkast]

ipa is sweet
don't worry about the acid either if you don't have it.

[Un_Chambered]

Thanks hk
Curious as to what you mean when you say its ok to leave out the acid?
would the procedure then yeild phosphite salts which can be used to reduce as well?
or more likely swic is terribly confused.just curious swic isn't leaving acid out.

[halfkast]

I meant

Now I'm tellin you that HCl must bee used in the procedure as is to convert the foliar shit to H3PO... NOTHING has changed here, right?

But I'm also telling you that HCl may bee used as a device to salt out KCl.

But if you don't have it alcohol will work great to salt out the KCl...

And ima also tellin ya that fan/a/c method of drying is a sack of gold nuggets of purity.

[Un_Chambered]

As you wish massstaa!
swic is following your write-up to a t other than ipa as OH,no dillution of foliar solution or HCl(aq),and room temp. evap followed by tupperware dessicator w/NaOH.
Input on drying bee's?

[halfkast]

all thats cool.

after using de-humidification
and fan at rT to evaporate off "free moisture".

Throw it in the freezer and think about if its worth trying to dehydrate completely.

I mean, a fan and A/C will get most of the water out inflicting little damage to even the surface of the H3PO3.


No NaOH dessicant, it will effect your H3PO3 by reacting with it to form sodium phosphite salts.

warm it on a hotplate during the fan drying if you want to speed things up and cause more complete dehydration. Then straight to a cool dry place.

The freezer will make it nice and hard for transferring to a permanent container.

[Un_Chambered]

Hey all
swic has been messin around with this.
Three attempts have left him with what is obviuosly some phosphorous acid combined with a black viscious fluid that stubbornly refuses to be seperated.
The foliar solution he is using states:
Total nitrogen..........................10%
(urea nitrogen)
available phosphoric acid(P2O5).........10%
soluble potash(K2O)......................5%
sources:Urea,Phosphoric acid,Muriate of potash
Any ideas on what's going wrong here folks?
Swim would like to make this brand work as its available locally.He has tried IPA and MeOH washes with little result.
He has also tried seperation using temp but the liquid is just too thick to seperate.
Any other bee's run into this?

[Osmium]

There obviously isn't any H3PO3 in it.

[halfkast]

its looking that way. to say the least.

dude finish the procedure and collect the H3PO4. Its not a HI recylcer like H3PO3, but it can be used to create HI.

[spectralshift]

When scaling up, greater effort and time should be spent on salting out the KCl it's been discovered.

Another important note is viscosity, when the viscosity of the solution of H3PO3, KCl, H2O and ALky is viscuous, KCl will actually precipitate, a) but much of it will not be able to be filtered out, and b) it won't sink to the bottom as a white layer.


Signs of an overly viscuous solution are a cloudy solution, and perhaps not even any sign at all of a bottom layer (KCl, always KCl, this isn't H3PO3 that has sunk).

The cure if your in this situation is more alcohol, and even a splash of HCl solution if it's on hand. This is followed by a good shake, and generous amount of time to settle at room temp.

As you add more alky to a cloudy one-layer solution (overly viscuous, KCl suspended in H3PO3 solution) you'll gradually see a formation of two layers, KCl on the bottom, and a liquid layer of you-no-what with a slight yellow tinge.

Another thing that works really nicely is sitting the wine bottle in a bath of hot water for a few minutes and then sitting it at room temp to settle...this acheives a formation of layers without addition of further alcohol.

When you've got two layers, this is the time when the solution can bee filtered without clogging.

When it's all cloudy, filtration is primarilly a No-go. two layers good, one layer bad - remember that.


After a filtration session, let it settle and you may see even more KCl precipitate out of the filtrate. So it's not a one-go-show! But don't worry, the H3PO3 is out of harms way so you can take as much time as you like.

If you are desperate for some H3PO3 for a RXN or to put on the garden, just pour a little of the motherload being worked on in to a small bottle and work on it separately OK?
Good.  

You can make it ultra pure really quickly when working with small amounts too...A splash of alkly and a splash of HCl, a dip in a bath of hot water, then time to settle will crash out everything when working with small amounts.



For ghetto drying, I think it's best to use the fan and or an air-con to remove the majority of the free-water, harming the H3PO3 none.
Then use the fan forced for a few minutes..preheat it, because if it isn't pre-heated it will tend to absorb water on the way up to temperature.


OK, finally isopropyl alcohol, TRY it. The story is that during testing, iso was used in one instance and I've got the sneaking suspicion it worked really nicely to salt out KCl. Someone upthread said that he'd been told to use iso, so those people may have had better information there, but I could only be sure on the metho tests, and so this is what I included in the write-up.

I would say that greater molecule sizes would work better,
Ill try to get more information here on alcohol molecule diametres etc.

To some up:

viscosity=bad for filtration & KCl settling out. Cure: more alcohol, a dip in a hot water bath.

10x
halfkast

[spectralshift]

A very small quantity of MgSO4 was used during the KCl precipitation phase, (that was experimental and the idea was to precipitate out a lot of KCl with very little MgSO4, that experiment was inconclusive and not what I came to tell you about.) at the end of the final drying stage a strong rotten egg gas smell, H2S was noted.

HCl was used in excess as a further KCl precipitation technique, (not advised anymore really, for THAT)

By this point I was just thinking that the addition of MgSO4 was a bad idea. The following day the prepared H3PO3 seemed a horrible dark honey colour, believed to be impurities. The smell was still strongly present aswell, and it tended to shit one to tears, and in fact it was returned to the oven in the hopes of driving off the H2S, any remaining HCl and hopefully clarify the colour.

This clarification just didn't occur, the solution became a very dark, much darker, almost black, which was disappointing.

So I checked out the merck entry for H2S in the hopes of shedding some light on how to remove it.

Properties:  Flammable, poisonous gas with characteristic odor of rotten eggs, perceptible in air at concns of 0.02-0.13 ppm, sweetish taste. Burns in air with pale blue flame. Ignition temp 260degrees. Explosive limits when mixed with air: lower limit 4.3% by vol, upper limit 46% by vol. mp minus85.49degrees ; bp minus60.33degrees : Giauque, Blue, J. Am. Chem. Soc. 58, 831 (1936) . Heavier than air; 1.5392 g/l (0degrees; 760 mm). d gas 1.19 (air = 1.00) . Vapor pressure 18.75 times 10 5 Pa. One gram H 2 S dissolves in 187 ml water at 10degrees, in 242 ml water at 20degrees, in 314 ml water at 30degrees; in 94.3 ml abs alcohol at 20degrees; in 48.5 ml ether at 20degrees. Sol in glycerol, gasoline, kerosene, carbon disulfide, crude oil. Water solns of H 2 S are not stable, absorbed oxygen causes the formation of elemental sulfur, and the solns become turbid rapidly. In a 50:50 v/v mixture of glycerol and water the precipitation of sulfur is retar ded considerably. pH of freshly prepd satd water soln 4.5. pKa 1 7.04; pKa 2 11.96. LC 50 in mice, rats ( ppm ): 634 , 712 (1 hr inhalation ) (Vernot) . LC 50 in rats ( ppm ): 444 (4 hr inhalation ) (Tansy) .

What I think is that H2S and H3PO3 stabilise eachother, especially when kept cool, and the H3PO3 stops too much elemental S from precipitating, and maintaining a good amount of H2S dissolved and fused with it. Similar to how glycerol does. That's what I suspect...but I KNOW that it contains H2S.

I KNOW that a small amount of MgSO4 is all that is required to produce this effect.

Someone else knows that, H2S is liberated during a reaction when H3PO3 is prepared like this.

This is so fucken cool, do a search by halfkast, stimulants forum, and in the post content type either rotten or eggs, where I ask geezmeister if he's ever noted that particular scent at the beginning of a phos acid synth.

I had to re-write this, proxy packed up. I was so pissed off, this one lacks the emotion.

*laughs loudly and strongly from the belly*

[spectralshift]

After some thought this is what I suppose is happening

the MgSO4 is being reduced by the H3PO3, atleast when the concentration is high and with elevated temperatures to MgSO3 (sulfite).

The MgSO3 is also oxidised easily to the MgSO4, hindering the overall reaction and production of the end-product, H2S.

I'm not sure if the HCl (excess) plays any role to this point, but I'm semi-confident MgCl2 is formed, because flat leaflets have been seen after rapid cooling. but im still confident it's formed irregargless of whether these leaflets are it.

I wouldn't mind the idea of adding some easily oxidizable substancez to the H3PO3 solution throughout the procedure to try stabilise things (as I think H2S would), thing's like ascorbic acid solution perhaps.


unfortunetly, the H3PO3 being oxidised to H3PO4 by the MgSO4 is the problem, and I've got a feeling it takes quite a lot.
But I think it depends on if and when the excess HCl is able to take part.


Well I'm motivated, I opened a book last night. Heh it was meaningful. Sucker.