AndrewOfWallachia
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"Expired" Formalin - Help
I got a bottle of Formalin a while ago because I wanted to make some Hexamine but I never got around to it. I left the bottle of Formalin sitting in
the garage and now I noticed that it became cloudy, and some white precipitate covers the clear walls of the plastic bottle - *this is worrying*.
Thankfully, the bottle was never unsealed. What actually happened here? And how should I dispose of it if necessary?
Thanks in advance! o7
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Radiums Lab
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2 posts? Ok what you see there is polymer of formaldehyde called Paraformaldehyde.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Radiums Lab
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It is formed when formaldehyde is evporated slowly. Id recommend to filter it and add some H2O.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Radiums Lab
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The H2O should be added to the remaining soln to prevent further polymerisation. Dont add too much.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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bnull
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It was stored in a cool pace, wasn't it?
Actually, methanol is used to limit polymerization. Adding more water just helps to dissolve some of the polymer.
You can depolymerize it by heating in the presence of an acid or base.
@Radiums Lab, what browser are you using?
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Radiums Lab
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Quote: Originally posted by bnull  | It was stored in a cool pace, wasn't it?
Actually, methanol is used to limit polymerization. Adding more water just helps to dissolve some of the polymer.
You can depolymerize it by heating in the presence of an acid or base.
@Radiums Lab, what browser are you using? |
Oh, hi bnull. I meant that you need to add water to the filtered solution, since this polymerisation happens because of the formalin solution loosing
water.
If we add a bit of water to the filtered solution then we can limit the remaining solutions polymerisation for couple of days.
If you are performing acid or base sensitive experiment then the water method is perfect.
Oh and I used this phone to post the previous 3 messages, It has an inbuilt opera browser in it. I cannot post more than 1 line in a single post so I
did multiple posts.
[Edited on 25-8-2025 by Radiums Lab]
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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bnull
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| Quote: | | Oh and I used this phone to post the previous 3 messages, It has an inbuilt opera browser in it. I cannot post more than 1 line in a single post so I
did multiple posts. |
That's odd. Is it running a KaiOS or Jio's own OS?
Heating alone should do. If there is enough precipitate, save it. Paraformaldehyde takes much less space to store than formalin. I'm still considering
which one to buy, as my needs are not so urgent.
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Radiums Lab
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Heating formalin, I would not do that, a soln. is good for me. And Bnull this runs on Jio's OS.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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AndrewOfWallachia
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| Quote: Originally posted by bnull | It was stored in a cool pace, wasn't it?
Actually, methanol is used to limit polymerization. Adding more water just helps to dissolve some of the polymer.
You can depolymerize it by heating in the presence of an acid or base.
@Radiums Lab, what browser are you using? |
...Yep. It was. I know full well Formalin shouldn't be exposed to cold, and I did not intend to expose it, my garage was fine in temperature when I
got it, but since I didn't get around to using it, it got cold over the winter.
So. You're saying, filter the paraformaldehyde out of the formalin, and then add water to the filtered formalin? (If I had some halfway decently pure
methanol I'd use it to prevent polymerization as you said, but I don't.)
In that case, what is there to be done with the separated paraformaldehyde, since I don't feel confident depolymerizing it into gaseous formaldehyde
like you suggested.
Thanks for the answer! o7
[Edited on 27-8-2025 by AndrewOfWallachia]
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bnull
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My reading skills aren't what they used to be. @Radiums Lab suggested adding water to formalin after filtering the polymer out, which I
interpreted as adding water to the unfiltered solution.
Polymerization in formalin happens because of traces of formic acid that come either from the manufacturing process or from oxidation of formaldehyde
by dissolved oxygen, although how likely the latter is I don't know. Adding water would dilute the acid and slow polymerization for some time, that
much is certain. If you add a small amount of sodium hydroxide and leave the solution alone for a few weeks, I'm pretty sure, as long as the garage is
not arse-freezing cold, that it will all depolymerize and go back to solution.
Heating (not boiling, that is) the solution will speed up the process but, as it seems you don't need all of the formalin right now, just filter out
the polymer and store it still wet (no need to dry it) in a well-sealed flask. It will come in handy someday. Or put it in a bottle, add sodium
hydroxide and water and leave it alone. When your first bottle is over, there will be this one.
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Radiums Lab
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Adding a base to formalin would lead to slow Aldol reaction. Polymer does not form due to HCOOH.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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bnull
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Are you sure? J. C. Bevington, The Polymerisation of aldehydes, p.145:
| Quote: | Polymerisation in Solution at Normal Temperatures. Formaldehyde dissolves readily in water, polymerisation occurring to give
polyoxymethylene glycols of general formula HO.[CH2.O]n.CH2.OH where n probably can have values up to 12; if
n exceeds this value the polymer is insoluble in water. Cryoscopic measurements have shown that the degree of polymerisation decreases as the
concentration of the solution is decreased or as the temperature is raised, and that the process is reversible. The velocities of the polymerisation
and depolymerisation reactions have been measured by cryoscopic, interferometric, and dilatometric methods (the results have been summarised by Mark
and Raff) and have been found to be comparatively small.
In aqueous solution formaldehyde is believed to form the hydrate CH2(OH)2 very readily; evidence for the existence of this
hydrate is that the corresponding hydrate of chloral is stable, and that by using the isotope 18O it has been shown that oxygen is
exchanged quite readily at 20° between acetaldehyde and water, probably by means of the equilibrium
CH3.CHO + H2O <=> CH3.CH(OH)2
The growth of the formaldehyde polymer may result from a polycondensation; the simplest type of reaction is represented as
HO.CH2.OH + HO.CH2.OH => HO.[CH2.O]2.CH2.OH + H2O
and the general reaction as
HO.[CH2.O]p.CH2.OH + HO.[CH2.O]qCH2.OH =>
HO.[CH2.O]p+q+1.CH2.OH + H2O
Both polymerisation and depolymerisation are catalysed by hydrogen ions and the former may occur by the following mechanism:
HO.[CH2.O]p.CH2.OH + H3O+ => HO.[CH2.O]p.CH2+ +
2H2O
HO.[CH2.O]qCH2.OH + H2O => HO[CH2.O]q.CH2.O- +
H3O+
HO.[CH2.O]p.CH2+ + HO.[CH2.O]q.CH2.O- =>
HO.[CH2.O]p.CH2.O.CH2.[O.CH2]q.OH
The net reaction clearly can be represented by the general equation above. The mechanism of the depolymerisation is discussed in a later section.
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Also, from Walker's Formaldehyde, p.75:
| Quote: | | Dilute alkalies and acids markedly accelerate the rate of paraformaldehyde solution, which varies with pH in the same manner as the solution reactions
studied by Wadano, Trogus, and Hess (pages 34-36). The rate of solution as found by Löbering goes through a minimum between the pH values 2-5,
increasing rapidly on either side of these limits, as illustrated in Figures 13 and 14. |
Adding a small (we're not talking of grams here) quantity of hydroxide to the formalin solution in the presence of paraformaldehyde (the
solution as it is in the bottle) will help dissolve the polymer and slow down polymerisation. The rate of aldol condensation under such circumstances
will not be so high as to inutilize formalin.
A suggestion: test the pH of the solution.
J. C. Bevington, The Polymerisation of aldehydes, Q. Rev. Chem. Soc, 1952, 6, 141 (http://doi.o/10.1039/QR9520600141).
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Radiums Lab
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Yea after bnull said like for example previous post, I did a bit of digging and asked my chemistry professor too, according to many sources and my
professor( he has a PHD in polymer chemistry) formic acid does not affect the polymerization but some sources say it helps the formalin to not
polymerize and some sources say it catalyzes the polymerization. He said heating is enough to depolymerize it. He even stated that aldol condensation
will take place but in a very slow manner, often taking 2 to 3 years to notice a significant effect. Some sources even stated that formalin oxidizes
into formic acid and methanol. Now I'm going to wait for bnull's research about these facts.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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bnull
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| Quote: | | Now I'm going to wait for bnull's research about these facts. |
Hold your horses. As far as my curiosity goes, with two reliable sources (that include other sources as well) and a plausible mechanism for
polymerisation in acidic media, I'm satisfied. You may want to provide sources for these other facts.
Edit: I see now how methanol inhibits polymerization. There are only two places in a polymer chain that the monomer can attach to and, if both are
protected by a methyl ether group, the monomer does nothing to it. It's like those caps one puts at the end of a pipe; there's no way to attach
another pipe to it if the two ends are capped. Maybe even ethanol works as inhibitor.
[Edited on 29-8-2025 by bnull]
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angrygiraffe
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You'll see cloudiness and sediment because it wasn't stored properly.
I wouldn't recommend using it anymore—those chunks mean some formaldehyde has turned into paraformaldehyde, which really cuts down its germ-killing
and preserving power.
Let nature take its course,without comparing anything!
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