Sciencemadness Discussion Board

40% formaldehyde solution from paraformaldehyde?

LD5050 - 9-10-2017 at 09:21

I need a 40% formaldehyde solution but I only have paraformaldehyde, how could I make the formaldehyde solution with the paraformaldehyde is this possible?

JJay - 9-10-2017 at 09:38

Wikipedia says so you would use 37 grams of paraformaldehyde in 63 mL of water.

LD5050 - 9-10-2017 at 13:11

Thanks JJay but if I remember right I think in order for the paraformaldehyde to dissolve you need to add a base like sodium hydroxide but if I do this I'm affraid it might interfere with what I need it for.

100PercentChemistry - 9-10-2017 at 14:39

Do you mean how to dilute it or actually making it?

ninhydric1 - 9-10-2017 at 16:03

Destructive dry distillation of paraformaldehyde yields the gas; heating paraformaldehyde in water produces a solution of formaldehyde.

EDIT: The second process would take more time in order to prevent the water from boiling.

[Edited on 10-10-2017 by ninhydric1]

[Edited on 10-10-2017 by ninhydric1]

Melgar - 10-10-2017 at 05:01

The hydrolysis is acid-catalyzed for sure. I don't know about it being base-catalyzed, although a base would definitely catalyze the Cannizzaro reaction, giving methanol and formic acid.

Diachrynic - 22-10-2017 at 11:33

I did a quick google search, and I got conflicting information.

The English Wikipedia says:
Quote:
Paraformaldehyde can be depolymerized to formaldehyde gas by dry heating and to form a formaldehyde solution by water in the presence of a base or heat.


But the German Wikipedia says:
Quote:
Es handelt sich um ein weißes Pulver, das bei niedrigem pH-Wert oder unter Erhitzung wieder in Formaldehyd aufgespalten wird.


which roughly translates to:
Quote:
It is a white powder, that upon heating or at low pH splits up again into formaldehyde.


But low pH means acidic! What now?

macckone - 22-10-2017 at 13:06

A base will catalyze paraformaldehyde to formaldehyde conversion. At high temp, it moves toward formaldehyde while at low temp (near 0C) it moves toward paraformaldehyde. Higher concentration causes paraformaldehyde precipitation.

Acids catalyze the trioxane to formaldehyde conversion.

Neutral solutions prefer paraformaldehyde rather than trioxane.

The equilibrium is impacted by concentration and temperature of the reactants in either case.

Remember that catalyst generally impact reaction speed
not direction. In this case the hydroxide and hydronium
ions can impact the form of the polymer due to two
competing polymer forms of the base unit.

Tsjerk - 22-10-2017 at 13:19

Just mix the para and water and stirr for some time. If it doesn't dissolve (I only made 25%), heat a bit.

S.C. Wack - 23-10-2017 at 13:25

Reflux.

Some polymers dissolve easily. Depolymerization at pH 6-7 is the same as below 1, except for the acid. It is said that the dissolving is much more difficult in between that.

LD5050 - 5-11-2017 at 11:41

Quote: Originally posted by JJay  
Wikipedia says so you would use 37 grams of paraformaldehyde in 63 mL of water.


Is that 37g para for 63ml h20 or did you mean 3.7g of para?

37g for only 63ml of h20 seems like a lot

JJay - 5-11-2017 at 12:53

37g... it's for 40% v/v. For 40% w/w you would use 40 grams paraformaldehyde and 60 mL water. 40% is very concentrated.

Disclaimer: I've never even taken my paraformaldehyde out of the package.

Diachrynic - 6-11-2017 at 10:26

Does anyone here know if paraformaldehyde is regulated in the EU, more specifically Germany?

I saw one offer on ebay.

It is a carcinogen (or the HCHO is), so it is not a nice thing. But you can make some nice things with it.

How is the legal standpoint of paraformaldehyde? Just because it is on ebay doesn't mean it is allowed here. I didn't find anything, so I'm asking here.

EilOr - 13-12-2017 at 02:18

Quote: Originally posted by Diachrynic  
Does anyone here know if paraformaldehyde is regulated in the EU, more specifically Germany?

I saw one offer on ebay.

It is a carcinogen (or the HCHO is), so it is not a nice thing. But you can make some nice things with it.

How is the legal standpoint of paraformaldehyde? Just because it is on ebay doesn't mean it is allowed here. I didn't find anything, so I'm asking here.

No skull and crossbones and not listed (on any list!) = you can buy it
It has many legit uses and unlike Toluene, CHCl3 (for environmental reasons), KNO3, H2O2,... (explosives) and the GÜG-Chemicals (drugs) it's nowhere listed as far as I know
Though I would be careful with the seller (S3), he also sells very distinct chemicals with little to no other than illegal usage (especially some exotic substituted benzaldehydes), might be only a matter of time his customer database is captured by the authorities and they might knock at your door. Though if you only want to buy paraformaldehyde from them I wouldn't hesitate

[Edited on 13-12-2017 by EilOr]