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JJay
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Prussian Blue from Laundry Bluing
Today I decided to boil down some laundry bluing to see if I could recover any ferricyanide compounds from it. I used an 8 oz (227 mL) bottle of
bluing and simply heated it gently on a hot plate with stirring.
So far, I have removed about 3/4 of the water. The bluing has taken on an appearance very similar to blue ink used in pens, and there is some very
fine precipitate.
One thing that I have noticed - the solution has a very weak almond odor... I'm told that cyanide smells like almonds. The MSDS for this variety of
bluing says that it is nonhazardous but warns not to mix it with acids. I can't confirm it, but I believe that the ingredients are water, Prussian
blue, oxalic acid, and ammonia.
Heating will likely gradually drive off the ammonia... I do have a respirator, of course, but before I evaporate to dryness, I suppose I ought to ask:
Does oxalic acid react with Prussian blue to produce hydrogen cyanide?
[Edited on 11-3-2016 by JJay]
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JJay
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I ended up boiling it down and obtained a few grams of a tarry, extremely blue substance that is mostly soluble in water.
My next move is to calcine it to destroy any oxalic acid compounds.
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ave369
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I think, hot concentrated oxalic acid could produce a small amount of hydrogen cyanide. But it's probably cyanidophobia on my part.
[Edited on 11-3-2016 by ave369]
Smells like ammonia....
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JJay
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I believe that is exactly what happened, but I don't believe that dangerous amounts were produced... just enough to create a noticeable odor.
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Boffis
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Laundry bluing often contains ultramarine and the reason it should not be mixed with strong acid is because it gives off hydrogen sulphide. This
latter reaction allows easy distinction between the two pigments.
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JJay
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This particular brand is widely believed to contain Prussian blue... It is Mrs. Stewart's.
I suppose I could do some tests.
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Daffodile
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Could you distill with acid into huge excess of aqueous potassium Hydroxide, add Ferrous Sulfate, and collect pure Prussian blue precipitate? That way
you can measure purity.
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JJay
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Quote: Originally posted by Daffodile  | | Could you distill with acid into huge excess of aqueous potassium Hydroxide, add Ferrous Sulfate, and collect pure Prussian blue precipitate? That way
you can measure purity. |
I have been thinking about doing something along those lines, bubbling gas produced with sulfuric acid and the blue compound through a hydroxide
solution and reacting with ferrous sulfate... of course, that is a fairly dangerous procedure since it involves creating hydrogen cyanide as an
intermediate.
As a test for hydrogen sulfide, I could try bubbling the gas through copper sulfate solution to see if a precipitate is formed. This is also pretty
dangerous, not to mention smelly.
[Edited on 12-3-2016 by JJay]
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JJay
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I pulled this experiment out of the cabinet today to look at finishing it up, and I noticed that long, white needles had grown out of the blue
substance. I'm not sure what these are, but they appear to be crystalline.
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fluorescence
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Interesting, depends on where you stopped your cleaning process. If you washed everything in the end most of the soluble parts should be driven off as
well. Although the original post seems to be somewhat older I'd just like to mention that this particular idea that HCN smells like Almonds is kinda
dangerous.
To be honest I have no idea what fresh almonds actually smell like. I worked with stuff like Benzaldehyde and they all smell completely different to
what HCN actually smells. It's very characteristic, since I have to work with it quite often I do tests once every 2 weeks where I have a small bottle
with a tiny amount wet KCN in there to test if I can still smell it and to remember the exact smell it has. I could probably detect it very fast by
smell since as said its very characterisitc but I have never smelled anything else that would resemble it afterwards.
With HCN it's like with H2S, you can smell actually quite tiny traces of it already although H2S can be detect in like 10.000 times lower conc. Still
you will smell the difference between a tiny conc. and a larger one. I had the unpleasant experience, more than once actually, to smell a larger
amount of HCN and then it's like HCl or HF, a larger amount is really irritant to your nose. Its really like breathing above a bottle of HCl. So yeah
I don't have oxalic acid to test it for you but as long as you work under a fume hood or outside you should be fine I guess, no guarantees!
[Edited on 27-4-2016 by fluorescence]
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JJay
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The almond smell is a bit hard to describe... it smelled like a watery artificial almond smell rather than like almonds. Unlike bitter almond
flavoring (which doesn't smell like almonds but does smell delicious), it didn't smell like anything that would be particularly good to eat, although
the smell was similar.
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fluorescence
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Mhm okay. I'd have to smell it. I once tried some artifical bitter almond oil and the smell was different as well.
We had that topic quite often what to do to actuall help people identify it. I thought of a wet q-tip that you hold for a short period of time into
some HCN vapour and that can be send to other members but it didn't really work out.
Best would be to avoid such experiments. Like Prussian blue can be easily made and just washing it multiple times should clean it enough. What would
you need a perfectly clean sample for ?
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JJay
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I can easily make Prussian Blue, but in this case I am trying to isolate it from OTC compounds. I am very curious about what the white needle-like
crystals I am seeing are. My cell phone camera doesn't really do them justice....
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fluorescence
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Have you checked them under a microscope to see how many different compounds there could be ?
I don't know what other compounds were in that OTC product you used.
I boiled Prussian Blue once in nitric acid. There is a very old paper on so called Prussian Green or Berlin Green a compound that should form when PB
is boiled in Nitr. Acd. or Chlorine. I tried it and it became really green but in the end blue particles formed and it became all blue again, seems to
be pretty reversible so I think some boilin will actually reduce the particle size. So not all acids seem to react with it I guess. Not really a fan
of this compound anyway. I work a lot with d-Metal Cyanides but I avoid Iron for many reasons.
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Artemus Gordon
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| Quote: Originally posted by JJay | | I can easily make Prussian Blue, but in this case I am trying to isolate it from OTC compounds. I am very curious about what the white needle-like
crystals I am seeing are. My cell phone camera doesn't really do them justice.... |
The Mrs. Stewart's site doesn't make it easy, but if you poke around long enough they tell you MSB is a colloidal suspension of ferric
hexacyanoferrate in water with a small amount of a biocide/algaecide and a "pH buffering agent".
My guess is your crystals are of this pH buffer, and I suspect it is sodium carbonate. Have you tried to find the pH of these crystals?
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JJay
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| Quote: Originally posted by Artemus Gordon | | Quote: Originally posted by JJay | | I can easily make Prussian Blue, but in this case I am trying to isolate it from OTC compounds. I am very curious about what the white needle-like
crystals I am seeing are. My cell phone camera doesn't really do them justice.... |
The Mrs. Stewart's site doesn't make it easy, but if you poke around long enough they tell you MSB is a colloidal suspension of ferric
hexacyanoferrate in water with a small amount of a biocide/algaecide and a "pH buffering agent".
My guess is your crystals are of this pH buffer, and I suspect it is sodium carbonate. Have you tried to find the pH of these crystals?
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Where do they say that it is a colloidal suspension of ferric hexacyanoferrate?
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JJay
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| Quote: Originally posted by fluorescence | Have you checked them under a microscope to see how many different compounds there could be ?
I don't know what other compounds were in that OTC product you used.
I boiled Prussian Blue once in nitric acid. There is a very old paper on so called Prussian Green or Berlin Green a compound that should form when PB
is boiled in Nitr. Acd. or Chlorine. I tried it and it became really green but in the end blue particles formed and it became all blue again, seems to
be pretty reversible so I think some boilin will actually reduce the particle size. So not all acids seem to react with it I guess. Not really a fan
of this compound anyway. I work a lot with d-Metal Cyanides but I avoid Iron for many reasons.
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No... I have not checked them under a microscope.
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Artemus Gordon
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| Quote: Originally posted by JJay | | Quote: Originally posted by Artemus Gordon | | Quote: Originally posted by JJay | | I can easily make Prussian Blue, but in this case I am trying to isolate it from OTC compounds. I am very curious about what the white needle-like
crystals I am seeing are. My cell phone camera doesn't really do them justice.... |
The Mrs. Stewart's site doesn't make it easy, but if you poke around long enough they tell you MSB is a colloidal suspension of ferric
hexacyanoferrate in water with a small amount of a biocide/algaecide and a "pH buffering agent".
My guess is your crystals are of this pH buffer, and I suspect it is sodium carbonate. Have you tried to find the pH of these crystals?
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Where do they say that it is a colloidal suspension of ferric hexacyanoferrate? |
<a href="http://mrsstewart.com/wp/wp-content/uploads/2013/02/Salt-Crystal-Garden.pdf">Salt Crystal Garden pdf</a> page 2.
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JJay
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Ok, so it is definitely largely Prussian Blue.
Here is what I got after I boiled down one bottle of it and allowed the moist solids to air dry. There are some long needle-like crystals that look
almost like white hairs.
[Edited on 5-5-2016 by JJay]
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Artemus Gordon
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Nice picture!
Those crystals are much thinner than I'd assumed. Maybe they are CaCO3. I would try touching a pH strip dampened with distilled water to one or two of
them. That would both tell you the pH and it would give you an idea of the solubilty. Did the crystals start to form early or late in the dehydrating
process?
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JJay
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| Quote: Originally posted by Artemus Gordon | Nice picture!
Those crystals are much thinner than I'd assumed. Maybe they are CaCO3. I would try touching a pH strip dampened with distilled water to one or two of
them. That would both tell you the pH and it would give you an idea of the solubilty. Did the crystals start to form early or late in the dehydrating
process?
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I think they formed late... they are very soluble and very acidic... as acidic as they are, I think they must be oxalic acid or perhaps sodium
hydrogen oxylate.
[Edited on 5-5-2016 by JJay]
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Artemus Gordon
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That's interesting. I assumed the biocide would need an alkaline environment. What pH did you measure?
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JJay
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I measured pH 1, touching the paper directly to the crystals. This does indicate strong acidity, if nothing else.
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PirateDocBrown
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I'm going to try this as well. I did a bit of digging, and one of the MSDS's on Mrs. Stewarts listed the ingredients (but not the proportions):
Water
Gluteraldehyde
Oxalic Acid
"pigment"
Other things I found said the gluteraldehyde replaced formaldehyde, so that they could continue to say they were "non-toxic". How oxalic acid jibes
with that, I don't know.
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JJay
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I never got around to actually calcining it (at least I haven't yet), but I have the Prussian Blue sitting in a vial close at hand.
I'm pretty sure that heating it above a few hundred degrees will drive off the impurities.
Edit: A pharmacist I know who has a master's degree in chemistry thought that was a dangerous idea, so I held off on it, but I'm really not seeing how
that would be dangerous. I mean, if you allow yourself to get a faceful of hot oxalic acid vapor, you'll wish you hadn't, but really, how dangerous is
it to boil down some laundry bluing and heat it in a crucible....
[Edited on 7-2-2017 by JJay]
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