Cat_got_my_tungsten!
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Sodium acetate discoloration
Sodium acetate having been heated via stovetop/teflon pan to remove water from what was formerly a solution of sodium bicarbonate and 5% distilled
white vinegar, had towards the very end of dehydration turned a yellow hue. This happened cheifly to the hydrated salt under the dry salt losing the
last bit of the water. NaHCO3 in bottom of pan, CH3CO-OH added until no more reaction was observed. -> then boiled till dryness. My query is what
caused the discoloration? This was not apparent with other salts I have seen elsewhere.
P.S. Rubber spatula to stir while in solution, wooden spatula to scrape from pan.
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YT2095
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a lot of food grade vinegars have sugars in them too.
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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Fleaker
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If it wasn't distilled white vinegar or glacial acetic, then that might be why you got that color-the sugars were probably caramelizing.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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guy
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I got the same problem using distilled vinegar too.
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garage chemist
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Sodium acetateis not truly anhydrous until the solidified salt has been melted (ca. 330°C)- you need to do this to your product, else reactions
calling for anhydrous sodium acetate will fail.
The dehydration and melting can cause discoloration even with reasonably pure chemicals. This is no cause for concern.
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chemkid
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When i was working with sodium acetate mine melted to a brown syrupy liquid. I presume the color is from impurities (also using vinegar and baking
soda) but my question is will this liquid once cooled turn back into crystals or just harden to a blob in my beaker?
Chemkid
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Ozone
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Was your teflon coated pan *perfectly* clean? If not even traces of adhered material will cause the discoloration. Caramelization of sugars too
(nevermind what might happen with traces of protein).
Does anyone know about how much iron might be present in vinegar? I would do the test (o-phenantholine), but I must finish mowing the lawn in the
infernal heat in crawfish town (and I noticed that my o-phenanthroline reagent has turned brown, which means I have to obtain and make more ).
Traces (that is, even ppm) of iron have cause me to have problems with the acquisition of totally white crystalline products.
Nevermind oxidation...
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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Cat_got_my_tungsten!
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Fantastic, thanks for the great suggestions. I have 1-bromo-3-chloro-5,5-dimethyl hydantoin lying around and through my past experiments I have found
that isopropyl alchohol effectively liberates what i am assuming to be Br2 & Cl2. Then the hot, brominated solution of Isoproplyl alcohol goes
from reddish bromine color to clear. Could this mean that the bromine/chlorine has replaced either the hydroxyl group or one of the hydrogens? After
leaving it set i see that the soulution had crystallized. Now if it had produced isopropyl bromide, the sodium acetate would then hypothetically
produce isopropyl acetate and sodium bromide. I am concerned though that having all that dissolved hydantoin in the solution would create some sort of
a problem. Would this be practical to expect somthing along these lines?
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chloric1
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I might be srong but---the hydantoins they use for spas are fairly insoluble substances. I do know that the bromine and chlorine are loosely bound
and are probably consumed in the reaction. The crystaline deposit is more than likely dimethylhydantoin. Look up the solubility in CRC Handbook or
Lange.
It is very doubtful that you have any isopropyl bromide as your halogen compound is a powerful oxidizer. Does the liquid in question have a stinging
eye burning odor? It may be a complex mixture of chloro & bromo acetones
You need a reducing proton acceptor to get alkyl halides like Dimethyl Formamide if you want to use halogenated cyclonitrogen compounds.
Fellow molecular manipulator
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not_important
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| Quote: | | Volatile components in the vapors of natural and distilled vinegars were identified by gas chromatography by comparing their retention dumes with
compounds of known composition and by functional group analysis. Twenty-five volatile components were identified from three natural vinegars (cider,
19 components; wine, 17 components; tarragon, 20 components), and 11 volatile components were identified from five samples of distilled
vinegar. Four components were present in all vinegars tested: acetaldehyde, acetone, ethyl acetate, and ethyl alcohol. The natural vinegars
had the largest number of volatile components. This was attributed to the nature of the fermentable carbohydrate material used for production of the
alcohol subsequently used for vinegar manufacture (e.g. apples and grapes). The importance of the earbonyls, alcohols, and esters to vinegar flavor is
discussed. |
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2621...
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MagicJigPipe
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I tried the vinegar/bicarbonate reaction in a "clean environment" with distilled white vinegar. Then I boiled the solution to dryness. I got a
mixture of about 50% pure white NaCH3COO and 50% off-white to dark brown colored, syrupy (some of it crystalline though) goo. I thought, well maybe
this was the normal discoloration that garage chemist mentioned. So, I dissolved it in a little bit of distilled water to see if it would be clear
but it turned dark brown.
So, I concluded that even in distilled vinegar there appears to be sugar of some sort (the brown NaCH3COO had a slightly sweet vinegar smell). Unless
the acetate decomposed but I'm pretty sure I didn't reach that temp.
Sauron, I request that you do not reply to this unless you are going to remain objective and not speak condescendingly to me.
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not_important
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I don't think it is sugars in the distilled white vinegar, sugars are just not that volatile. I think it is aldehydes and ketones condensing into
gorp.
From the times I've played with this, you get less discolouration if you let the solution evaporate and room temperature or slightly above, maybe
helped by pulling a vacuum on the solution. The brown colouration is soluble in isopropyl alcohol, acetone and MEK, and ether; this suggests
compounds with low ratios of hydroxy groups - condensed unsaturated compounds.
If you kept under 150 C the acetate shouldn't have decomposed, SFAIK.
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MagicJigPipe
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You know what. I never thought of that. And I know that sugars won't distill over but I have no idea of the manufacturing process and thought they
might add some in the process. I just got done letting some NaAcetate solution evaporate and there is no discoloration but it seems to only dry to a
certain point and then remain wet. I'll try using a dessicant and/or a vacuum.
[Edited on 28-9-2007 by MagicJigPipe]
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MagicJigPipe
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I did a little reading since my last post and discovered that some "distilled" vinegars don't actually mean that they distilled the actual vinegar but
the ethanol used to make it.
I'm not sure of the commercial process most often used to oxidize the EtOH but I know one of them is the bacteria method.
Also, there is something called "mother of vinegar" that forms in old bottles of vinegar which is a brown goo of acetic acid bacteria and cellulose.
Could heating vinegar speed up it's formation?
[Edited on 8-12-2007 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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MagicJigPipe
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Ok, this time I used generic vinegar (Kroger brand) instead of the Heinz brand and I only used a pint of vinegar in a 8x8 pan. I heated at 176*C
until it was about a cm from the bottom of pan. Then I took out the hot saturated solution, let it cool and let the NaAc crystals form. Then I put
it back in and heated at 135*C for a few more hours while stirring the crystals around occasionally. I got very little discoloration. Light yellow
instead of dark brown. That's the way I'll do it from now on.
And the hot saturated solution wasn't brown like usual. It was light milky white.
US to Metric
8x8 = 20.32cmx20.32cm
pint = 473.176475mL
*EDIT*
Dissolving in water and vacuum filtering seems to remove some gunk. Almost too much trouble for such a cheap substance.
[Edited on 12-12-2007 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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MagicJigPipe
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Okay, I figured out what the brown sticky crap probably is. This guy wrote an article on the production of vinegar and it's true--"distilled" white
vingegar means the EtOH used to create the acetic acid is distilled, not the vinegar itself. He seems to know what he is talking about.
http://www.nowheat.com/fooddb/food/vinegar2.htm
In the quote below he is talking about what the "distilled" vinegar is likely to contain as far as "nutrients" go:
"The nutrient mixture is said to consist of a variety of salts and some carbon and nitrogen sources such as glucose, citric acid, ammonium phosphate,
some yeast extract or dried yeast, and hydrolyzed soy flour. At the conclusion of the fermentation the vinegar is not distilled, but rather is
filtered to remove microorganisms and particulate material and diluted to bring the acetic acid level down from values as high as 15 to 20% to roughly
5%."
My guess would be the glucose is causing the brown discoloration. What do you guys think?
EDIT
By the way, about the above post, after heating the solution to dryness the same gunky brown crap was obtained. Just less brown and "gunky".
[Edited on 4-18-2008 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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16MillionEyes
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I'm so glad someone posted information about this, I'm familiar with the brownish sodium acetate from white vinegar and sodium bicarbonate. The best
and by far more effective method of obtaining the pure acetate is to distill the vinegar (best twice) and then reacting it. Since I lack the proper
equipment to do so I've gone the straight way and it's afforded me a painful purification process for the acetate. Until now, after careful
crystallization and gravity filtration (I have no way of doing vacuum filtration) I get a nice white powder; half a gram so far from like 30-40 grams
(I don't have a balance either, I'm such a great chemist...).
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copperastic
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That happened to me to. Is there any way to remove the sugar?
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Etaoin Shrdlu
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Try crystallizing, washing with isopropyl alcohol, then recrystallizing.
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Brain&Force
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I think the problem may also be the source of baking soda - some "fridge scrubbers" have an air freshener in them as well. There may be a reaction
between one of the organics in each chemical. But this depends on the source of baking soda. The culprit is usually Arm & Hammer.
At the end of the day, simulating atoms doesn't beat working with the real things...
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S.C. Wack
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Arm & Hammer is USP grade. It's the vinegar. Do not boil anywhere near dry, lower the heat, be cautious. Etaoin Shrdlu's advice, though I don't
recall now what solvent I used. There are likely several other threads where it's all been said.
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Brain&Force
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There's one variant for odor scrubbing that contains an air freshening compound, but their all-purpose baking soda is perfectly fine.
At the end of the day, simulating atoms doesn't beat working with the real things...
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