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obsessed_chemist
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help purifying potassium hydroxide (drain cleaner)
I have 1/2 gallons of potassium hydroxide solution drain cleaner. The company msds states that the product is composed of 45% potassium hydroxide by
weight, the rest of the ingredients are inert, so I am assuming it's about 54-55% water.
A blue dye has been added to color the fluid blue, probably in order to discourage children from drinking it by mistake.
I added a tiny amount of 3% H2O2 and the dye immediately oxidized, turning pinkish-red. This lead me to believe that only a very small amount
of dye is added to the drain cleaner.
Is it possible somehow to extract this dye via a petroleum-naphtha wash or something?
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Magpie
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What you are proposing might work - try it on a test tube scale. You might also try using activated charcoal, available at some health food stores.
Then you would probably have to remove the carbon-dye by filtering through diatomaceous earth (swimming pool supplier)or some other filter media.
The single most important condition for a successful synthesis is good mixing - Nicodem
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roamingnome
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The preferred pigment is phthalocyanine blue.
A drain cleaning composition includes at least about 40% by weight of a free-flowing coated alkali metal hydroxide and about 5% to 20% by weight of
mixture of a hypochlorite
Liquid drain cleaners do contain 5 to 6% hypochlorite
Almost sheepishly giving the reference as
http://www.freepatentsonline.com/4664836.html
tossing the lot into the furnace will leave the inorganics you seek…
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Pyridinium
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| Quote: | Originally posted by roamingnome
tossing the lot into the furnace will leave the inorganics you seek… |
yeah I was going to say just roast the stuff down to calcined oxides (in this case, hydroxides- can't get K2O by simple roasting). The chlorine
would be gone, and the dyes would char into solid C, which could be removed after re-dissolving the KOH in water (carefully!) But it's a lot of
energy to put into something.
obsessed, I'm sure you don't need me to remind you, boiling alkali is brutal stuff. Full protective gear a must.
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obsessed_chemist
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| Quote: | Originally posted by roamingnome
The preferred pigment is phthalocyanine blue.
A drain cleaning composition includes at least about 40% by weight of a free-flowing coated alkali metal hydroxide and about 5% to 20% by weight of
mixture of a hypochlorite
Liquid drain cleaners do contain 5 to 6% hypochlorite
Almost sheepishly giving the reference as
http://www.freepatentsonline.com/4664836.html
tossing the lot into the furnace will leave the inorganics you seek… |
I found this:
"The phthalocyanine blue pigments are among the most stable in hydrogen peroxide solutions. Their substantivity has presented the problem of
discovering a way in which to prevent dye staining of any of the fabrics customarily laundered. In accordance with the invention it has been
determined that the addition of small quantities of selected surface active agents will prevent dye substantivity of phthalocyanine based blue
pigments."
http://www.freepatentsonline.com/3970575.html
From this I think we can be fairly confident that this is not the pigment (or for our purpose, adulterant) used in this particular drain cleaner,
since only a very small amount of dilute peroxide was needed to change the color to red/pink.
I think that the only "active" ingredient, and thus hazardous ingredient is potassium hydroxide. If it contained a hypochlorite, then I would
presume that their company (US based) would be required to then list this, but an inert and non-hazardous ingredient, in this case water, would not
have to be listed.
[Edited on 3/27/2007 by obsessed_chemist]
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obsessed_chemist
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Also found this from the Maine DEP website:
"Toilet bowl cleaners contain sodium hydroxide, chlorinated phenols and complex phosphates. These chemicals are toxic and corrosive. Long-term
exposure causes headaches, and liver and kidney damage. Some of these chemicals build up in fatty tissues of wildlife and humans. Products with blue
dye contain chromium, which is toxic."
Gee, that doesn't sound promising. Probably the same dye I'm currently dealing with. I know that blue anthocyins (like some of the ones found in red
cabbage) turn blue when exposed to peroxide. I'll keep searching.
[Edited on 3/27/2007 by obsessed_chemist]
[Edited on 3/27/2007 by obsessed_chemist]
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S.C. Wack
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Sounds like a product sold at Kmart which does not contain hypochlorite. The amount of dye in that product is small; and if the bottle is left
uncapped it presumably absorbs some CO2 (without precipitation of carbonate, however), turns colorless, and deposits a filterable rust-colored solid
IIRC.
Not a whole lot of CO2 was absorbed by the time all the dye been oxidized(?) and precipitated, and the filtrate did not exhibit signs of contamination
in use in many different (mostly inorganic) reactions.
[Edited on 27-3-2007 by S.C. Wack]
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obsessed_chemist
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Well, if activated charcoal was used to remove the dye or oxidized dye, why would it be selective, and not absorb potassium hydroxide as well?
Also, would it be ideal to add milled activated charcoal/carbon to a warm solution, then cool and filter through diatomaceous earth? I'm not real
familiar with using charcoal to filter other than pouring a solution through it.
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Pyridinium
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I don't think your dye contains chromium. H2O2 would produce blue perchromic acid, a very sensitive test. Although if Cr were present you might
first have to free it from the dye molecule.
Because you have a different but still fairly-strong color after addition of H2O2, I'm assuming you haven't destroyed the dye chromophore completely.
It's just in a different form. What happens when you add an excess of H2O2 to this material? Try it on a small sample.
The phthalocyanine structure is pretty stable and shouldn't undergo ring-opening under those conditions (I think). I found an oxidation experiment on
this molecule, but the conditions were deliberately acidic. I misplaced the link though.
For liver damage, it depends on what kind of chlorinated phenols they're talking about. Roasting your product down to calcined KOH would destroy all
that stuff anyway, just don't breathe the fumes in case a little KOH gets spattered into the airborne mist.
Activated charcoal doesn't bind KOH very well, thus it could be used to separate something like an organic dye. Just be aware that there are a few
types of activated C, depending on how they've been treated.
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obsessed_chemist
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Well, it's possible that the drain cleaner is a bit contaminated with hypochlorite, chlorate, and/or chloride, especially if it is produced via the
chlor-alkali process. In that case, the end product would still be contaminated with potassium chloride, even after roasting. I suppose that this
could be removed by dissolving the KOH in warm methanol, then decanting and evaporating on steam bath.
Oh, and to answer your question, the pink color remains, even after adding an exess of H2O2.
[Edited on 3/27/2007 by obsessed_chemist]
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obsessed_chemist
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| Quote: | Originally posted by S.C. Wack
Sounds like a product sold at Kmart which does not contain hypochlorite. The amount of dye in that product is small; and if the bottle is left
uncapped it presumably absorbs some CO2 (without precipitation of carbonate, however), turns colorless, and deposits a filterable rust-colored solid
IIRC. |
Well I tried to tell if the dye precipitated as a solid, but even if it had, it was such a small amount that it suspended well in the solution and it
looked like it could be dissolved. Wack, have you purified OTC caustic potash with success?
[Edited on 3/27/2007 by obsessed_chemist]
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not_important
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I'd do a small scale test before using diatomaceous earth as a filter. Remember that diatomaceous earth is effectively fine particles of silica, and
apt to react with strong alkali; filtering such solutions through fritted glass is one way to ruin the filter.
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obsessed_chemist
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^ Things always tend to get complicated when working with caustic/corrosive chemicals, having to take into account the compatability with said
chemicals and available containers/materials.
I think I'm gonna scrap the whole diatomaceous earth thing, and opt for the charcoal filtering. Any suggestions for charcoal filtering? I was going to
pick up 1 lb of activated charcoal for fish tanks, and set it up in one of those nylon reusable coffee filters (after testing it, of course), and see
if I can remove the dye by passing it through one or more times.
I suppose it would also be a good idea to try filtering a seperate sample of caustic-potash solution where the dye has been oxidized by a small amount
of H2O2, and see how this affects the filtering process.
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Pyridinium
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I did a bit of reading, and it sounds as though you might be converting the phthalocyanine from its beta form to its alpha form. The alpha form is
reddish in color but less stable.
Pthalocyanine is quite resistant to a lot of things, even to H2SO4 (and of course, alkali), but if you overloaded it with oxidizer in acidic solution
you would destroy it and end up with pthalimide.
Looking forward to hearing how the activated C works for this stuff.
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not_important
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Coffee filters are likely too coarse to do a good job in this case. Nylon might be OK, as you don't need to filter hot alkali. If you were to line
the coffee filter with fine sand it might work..
Usually you stir the charcoal with the solution for awhile, then filter off the charcoal. Just filtering through a relatively thin layer of no more
than a few cm doesn't give enough time for good removal.
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obsessed_chemist
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^ Well after reading the other thread about sodium silicate synthesis, I think I going to avoid using any kind of silica-based filter medium.
The coffee filters I'm referring to are a really fine nylon-like mesh, and are unlikely to let much charcoal through, especially if I wash the
charcoal first with distilled water to rid it of tiny particulates first. I just hope the filter will withstand the caustic conditions.
Since the amount of dye in question is obviously very small, I'm hoping only a few grams or so will be required to clean about a liter's worth of
caustic potash solution. I could even line the bottom of said filter with a layer of washed charcoal, just for good messure.
Tomorrow I'll try to pick up everything I need for this qualitative experiment. Currently, I don't have access to any 27-35% peroxide to oxidize the
dye before filtering the second sample, but since very little is needed anyhow, 3% USP should be fine. I will use seperate charcoal for each trial
(one w/ dye as-is, and one post-oxization), and try everything at about room temperature, or between 20 and 25 deg celsius. HDPE will most likely be
the chosen container material for this experiment.
On a side-note, does anyone know if a stainless-steel tea-strainer will hold up okay in caustic solution?
[Edited on 3/28/2007 by obsessed_chemist]
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Magpie
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The activated carbon that I bought from a health food store is exceedingly fine. I think that's part of what makes it so effective. IIRC I used it
to take a purple dye out of some OTC phosphoric acid.
I see that a silaceous medium might not be the best for strong caustic. Whatever you use it will have to be very fine to take out the kind of
activated C I'm thinking of. Perhaps just regular lab filter paper (fine grade), which should be just cellulose, would work.
The single most important condition for a successful synthesis is good mixing - Nicodem
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12AX7
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Hmm...I should try making a strong NaOH solution, adding some crud and seeing if it drips through packed kaowool (an aluminosilicate fiber, I believe
with some magnesium around), a filter media I've been using quite successfully lately.
Tim
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obsessed_chemist
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| Quote: | Originally posted by Magpie
The activated carbon that I bought from a health food store is exceedingly fine. I think that's part of what makes it so effective. IIRC I used it
to take a purple dye out of some OTC phosphoric acid.
I see that a silaceous medium might not be the best for strong caustic. Whatever you use it will have to be very fine to take out the kind of
activated C I'm thinking of. Perhaps just regular lab filter paper (fine grade), which should be just cellulose, would work. |
Would that OTC phosphoric acid source happen to be concrete etchant? Seems that some of the more concentrated concrete cleaners/etchants happen to
also contain a marginal amount of 2-Butoxyethanol which would be very hard to seperate due to high boiling point (171 Cel), Unless it can be absorbed
by a non-polar solvent. Although apparently some of the etchants out their are nearly 85% concentrated Phosphoric acid which is intended to be diluted
before use. I just haven't found any yet (haven't gotten to the paint store yet).
Well, maybe I'll hold off on the experiment until I have a proper filtering medium. I'll look into the activated health-food quality charcoal as well
in the meantime.
[Edited on 3/29/2007 by obsessed_chemist]
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Magpie
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Yes, I believe it was a concrete etchant. And I did remove the organic crap using a non-polar solvent. This is documented in another thread.
I later found a much superior way to get phosphoric acid: make it with con H2SO4 and pottery grade Ca3PO4. This is also documented in another thread.
The single most important condition for a successful synthesis is good mixing - Nicodem
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obsessed_chemist
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^ Now if only there was an easy way to get H2SO4, other than professional rooter - grade. [A bit off topic:] For a while I was excited about the
proposition of electrolytic salt-splitting of say, rochelle salt, or sulfate of potash to obtain lye and sulfuric acid, but I soon realized that the
ion-exchange membrane technologies to keep the two end-products seperated are still very much in development, and a DIY home-device would be a
daunting task. [/end]
I'm heading out for supplies at the moment. Probably won't have the charcoal I need for a couple of days though.
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Magpie
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There is an easy way to get con sulfuric if you live in the US. All you need to know is: Rooto. Through Rooto all things are possible (well
almost).
The single most important condition for a successful synthesis is good mixing - Nicodem
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obsessed_chemist
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^ Yes but doesn't Rooto add a red dye, and Liquid-Fire also add a green dye? Let me guess; these too can be removed to purify our precious
ghetto-oil-of-vitriol?
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12AX7
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The red jug of 'fire I have is slightly yellowish. No apparent dye.
Tim
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UnintentionalChaos
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I use activated carbon sold for recharging fish tank filters. I assume that if its safe enough for fish, I dont plan on eating anything I make with it
anyway. It does need to be coffee milled/mortar and pestled though, since it comes in little chunks.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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