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?Praxichys - 8-12-2015 at 05:26
Has it seen low temperatures? Formaldehyde solutions polymerize at low temperature to form paraformaldehyde, which is less soluble.Deathunter88 - 8-12-2015 at 05:32
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?
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."
chemrox - 8-12-2015 at 13:19
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.ave369 - 9-12-2015 at 00:48
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.unionised - 9-12-2015 at 01:51
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. ave369 - 12-12-2015 at 04:28
