ave369
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Cloudy formalin
Recently bought a bottle of formalin. I was expecting it will be transparent, but is is cloudy and milky. It came it a PETF bottle. Is it normal?
Smells like ammonia....
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Praxichys
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Has it seen low temperatures? Formaldehyde solutions polymerize at low temperature to form paraformaldehyde, which is less soluble.
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Deathunter88
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Quote: Originally posted by ave369  | | Recently bought a bottle of formalin. I was expecting it will be transparent, but is is cloudy and milky. It came it a PETF bottle. Is it normal?
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Always a good idea to Google your question before posting it. 
I Googled "formalin is cloudy" and here are the first 3 results:
"The solid is likely to be paraformaldehyde and not trioxymethylen
(trioxane). Warming the solution in a 30 deg. C water bath should make it clear again, but it may take couple of hours."
"STABILITY: Formaldehyde may become cloudy upon standing, especially at cool temperatures. It slowly oxidizes in air. It is sensitive to exposure to
light [169],[295]. It is polymerized in aqueous solutions if unstabilized [169]. Solutions of it in water, DMSO, 95% ethanol or acetone should be
stable for 24 hours under normal lab conditions [700]."
"Formalin is a clear solution. Prolonged storage, exposure to direct sunlight or temperature below 5 degrees C of formalin results in the formation of
paraformaldehyde. Paraformaldehyde is highly toxic to aquatic life. Thus, formalin that appears cloudy, has a white precipitate on the bottom of the
container (to visualize swirl the bottle to suspend the precipitate) or has been in storage for a prolonged period should not be used for treatment of
fish."
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chemrox
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I have mine in the original bottle which was poly. I keep it in a cabinet where light exposure is minimal. I'm grateful for the post because I didn't
know most of the above. Keeping reagents at STP and protected from UV is a precaution with almost any reagent.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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ave369
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I left my bottle sit on top of a brick stove, where the temperature is near 30 C. The cloudiness diminished, paraform condensed into clumps and
precipitated. Now trying the water bath route.
Smells like ammonia....
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unionised
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I'm intrigued by the assertion that it's sensitive to light.
The stuff is colourless so it doesn't absorb (visible) light.
How does the light that goes through it unperturbed promote a chemical reaction?
For what it's worth, it doesn't absorb much in the near to moderate UV either; a peak near 280 nm IIRC.
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ave369
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Succesfully declouded my formalin.
Smells like ammonia....
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