deadrush
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Dithionite from product with naco3
I can't seem to think of a simple way of separating these two, (sodium dithionite and sodium carbonate). Anyone have a suggestion? BTW the product is
some color detergent from michaels.
Also, it always seemed to me that dithionite would make a great reduction agent. Am I wrong?
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Radiums Lab
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Quote: Originally posted by deadrush  | I can't seem to think of a simple way of separating these two, (sodium dithionite and sodium carbonate). Anyone have a suggestion? BTW the product is
some color detergent from michaels.
Also, it always seemed to me that dithionite would make a great reduction agent. Am I wrong? |
You can exploit their solubilities, according to my knowledge sodium carbonate is less soluble than dithionite. So u can boil the solution down to a
point where u can see sodium carbonate coming out of the solution and you can perform filtration. Repeat the same process for higher purity. I once
used dithionite to dye a cloth with indigo but I can't comment on its reducing nature.
[Edited on 18-3-2025 by Radiums Lab]
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Texium
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Thread Moved
18-3-2025 at 08:19 |
bnull
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| Quote: Originally posted by chloric1 | | I read that sodium hydrosulfite is insoluble in alcohol, and it salted out by NaCl and CaCl2. Other salts work too but I cannot recall. So gently
mix your product in minimal water at no warmer than 20 degrees C and add a solution of 30 grams of rock salt in 100 grams of distilled water and put
in the freezer. |
As for its qualities as reducer, see the EROS entry for sodium dithionite: | Quote: | | versatile reagent for reduction of aldehydes, ketones, unsaturated conjugated ketones, quinones, diunsaturated acids, azo, nitro, and nitroso
compounds, imines, oximes, tropylium salts, pyridinium salts, pyrazine, and vinyl sulfones; intramolecular Marschalk cyclizations, dehalogenation of
vic dibromides and α-halo ketones, Claisen rearrangement of allyloxyanthraquinones and for the synthesis of 8-arylaminopurines
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Keras
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Doesn’t really seem so. According to Wikipedia, the solubility of sodium carbonate is 164 g/L at 15 °C and sodium hydrosulphite is around 200 g/L
at 20 °C, which means that both are in the same ballpark.
You could try and neutralise your solution with acetic acid, until you don’t see any bubbles (pH ~ 6/7). Sodium acetate has a very high solubility
(1233 g/L at 20 °C) and so after boiling you should be able to precipitate quite a lot of pure sodium hydrosulphite. Don’t go too far, because
sodium hydrosulphite decomposes in acid solutions.
As for the reducing properties, I use it to reduce nitro groups to amine, but it can also be used to reduce Cu (II) to Cu (I) compounds, Fe (III) to
Fe (II), Cr (VI) to Cr (III), etc. It works very well with nitroso groups.
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Radiums Lab
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@Keras thanks for pointing out that there is a slight difference in their solubilities, i.e if we try crystallization we get a low purity product. But
there's a problem if we use acetic acid, we get low to very poor yields because sodium hydrosulphite decomposes. We can try the method which bnull
pointed out with very minimum impurities in the product.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Keras
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| Quote: Originally posted by Radiums Lab | | @Keras thanks for pointing out that there is a slight difference in their solubilities, i.e if we try crystallization we get a low purity product. But
there's a problem if we use acetic acid, we get low to very poor yields because sodium hydrosulphite decomposes. |
Yes, I know about decomposition. It should be minimised because the neutralisation of sodium carbonate by acetic acid creates a basic solution. pH of
[CH₃COONa] = 0.1 mol/l is around 9.
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RU_KLO
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from: INORGANIC SYNTHESES
VOLUME II
MCGRAW-HILL BOOK COMPANY INC.
1946
W. CONARD FERNELIUS
page 172
"
Sodium dithionate is recovered by concentrating the
solution on a steam bath. Successive crops of crystals are
obtained by cooling to about 10". These crystals are
filtered off, sucked as dry as possible, but not washed. A
precipitate, which may come down in the first concentra
tion, is removed by filtration from the hot solution before
cooling for crystallization. When the volume of mother
liquor has been reduced to about 10 ml., it is discarded
since most of the dissolved material in it is sodium carbonate.
The combined crops of crystals are spread out on
absorbent paper to dry at room temperature
.
In a preparation starting with 80 g. of Java pyrolusite
(90 per cent MnOz), 177 g. (88.5 per cent) of sodium
dithionate, Na2SzOs.2Hz0w, as obtained."
Attachment: inorganic-synthesis02-2 dithionates.pdf (748kB)
This file has been downloaded 11 times
Go SAFE, because stupidity and bad Luck exist.
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bnull
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It is sodium dithionite, Na2S2O4, that is in the mix. It wouldn't survive a steam bath. Sodium dithionate,
Na2S2O6, on the other hand, only decomposes if heated above 190 °C. You can't even oxidise it with permanganate. It
is interesting, anyway.
| Quote: | | the product is some color detergent from michaels. |
It isn't scented, is it?
Edit: I knew I had seen the suggestion given by @chloric1 somewhere else. Brauer's, pages 393-394:
| Quote: | Sodium Dithionite
Na2S2O4 * 2 H2O
Sodium dithionite dihydrate is prepared by salting out an aqueous solution of commercial Na2S2O4.
A 20-25% solution of the purest obtainable Na2S2O4 in air-free distilled H2O is prepared in an inert gas
atmosphere. The solution is filtered in the absence of air. Then 30 g. of finely powdered NaCl per 100 ml. of H2O is quickly added and
immediately vigorously shaken. After about half a minute, the dihydrate precipitates as a thick, white crystalline slurry. It is suction-filtered
(again in the absence of air) and washed with saturated NaCl solution, then with aqueous and finally with anhydrous acetone. The crystals are dried on
clay in an evacuated desiccator preflushed with nitrogen. Other salting-out agents include NaHSO3, NaOH, NaNO2,
CH3COONa, MgCl2, CaCl2 and ZnCl2.
Because of its instability, the dihydrate has no practical uses; anhydrous Na2S2O4 is used on a large scale as a
reducing agent in the dye industry, for preparing rongalite (CH2O*Na*HSO2*H2O) and as an O2 absorbent.
SYNONYM:
The older designation is "sodium hyposulfite," while in industry it is called (incorrectly) "sodium hydrosulfite."
PROPERTIES:
Formula weight 192.13. Colorless, needle-shaped crystals; very air sensitive; decomposes particularly easily when moist, forming
Na2S2O5 and Na2S2O3; strong reducing agent. Decomposes thermally to
Na2S2O3, Na2SO3 and SO2.
Readily soluble in water (2.18 g. of Na2S2O5*2H2O/100 g. of H2O at 20 °C); insoluble in
ethanol.
REFERENCE:
K. Jellinek, Z. anorg. allg. Chem. 70, 93 (1911). |
I'd say that the only viable salting-out agents are NaCl, NaHSO3, NaOH, NaNO2, and CH3COONa because of carbonate.
Edit2: Fixed typo.
Edit3: Zinc dithionite is soluble in water but zinc carbonate isn't. If the amount of sodium carbonate is small, you can remove it by adding some
soluble zinc salt, like chloride or sulfate. The solution would have a somewhat inert sodium sulfate or chloride (which wouldn't affect most of the
reductions with dithionite) and sodium dithionite.
You can also store it as it is and only purify it when needed. Or use it raw; carbonate doesn't interfere on organic reductions, does it?
[Edited on 19-3-2025 by bnull]
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Keras
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| Quote: Originally posted by bnull |
It is sodium dithionite, Na2S2O4, that is in the mix. It wouldn't survive a steam bath. Sodium dithionate,
Na2S2O4, […] |
Lol.
The latter should be Na2S2O6. :p
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bnull
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Yep, it is a typo. I forgot to change the number after copy-pasting the formula. 
Edit: The article by Jellinek, Über die Herstellung von reinem Hydrosulfit und über das System Hydrosulfit-Wasser (On the manufacture of pure
hydrosulfite and the system hydrosulfite-water, or something like that), is freely available at https://onlinelibrary.wiley.com/doi/10.1002/zaac.19110700108. 42 pages, with drawings.
[Edited on 20-3-2025 by bnull]
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