Sciencemadness Discussion Board

Formic acid prep?

Glu0n - 20-12-2016 at 00:59

My head hurts like hell right now. Spent the last 3 days of my free time trying to prepare some formic acid, i only need 1ml ffs. I don't want to spend $40 and wait 4 weeks for shipping.

Oxalic acid + Glycerol doesn't work. I don't know why i expected it to work this time when it didn't the last 3 times i tried. The distillate is maybe 1% formic acid, useless. All that comes over is water, until the allyl alcohol.

Permanganate and dichromate oxidise right to CO2.

Chloroform reacts with NaOH in methanol, seems like sodium formate is formed but can't isolate it from NaCl. Adding sulphuric acid is the same problem, no formic acid distils over and if it does its contaminated with HCl.

Paraformaldehyde with NaOH seems to give sodium formate. I added some 40% H2SO4 and there was a huge evolution of gas. I don't know if the headache is frustration or monoxide.

No stores sell any product with formic acid. What do i do next? Sodium bicarbonate and sodium borohydride? I don't know. Im sick of it.

Aqua-regia - 20-12-2016 at 01:57


Oxalic acid + Glycerol work well. Heat the mixture very slow and adjust the right teperature very carefully. Obviusly you overeheated the mixture.

Tsjerk - 20-12-2016 at 02:35

Electrolysis of formaldehyde?

Liamatpm - 20-12-2016 at 07:38

I would agree with Aqua-regia. But when the test does work don't spill it on your hand!

unionised - 20-12-2016 at 11:54

"Chloroform reacts with NaOH in methanol, seems like sodium formate is formed but can't isolate it from NaCl. Adding sulphuric acid is the same problem, no formic acid distils over and if it does its contaminated with HCl."

Calcium formate is a lot less soluble than calcium chloride.

Glu0n - 20-12-2016 at 14:50

Quote: Originally posted by Aqua-regia  

Oxalic acid + Glycerol work well. Heat the mixture very slow and adjust the right teperature very carefully. Obviusly you overeheated the mixture.


Had it in a boiling water bath for 4 hours, just water came over when i moved to mantle. I thought maybe i decomposed the formic acid keeping it hot for so long so next time i just distilled at a drip every second pace for an hour or whatever it took, still nothing significant. Watched the temperature in the still head and it was about 110-120.

Quote: Originally posted by Liamatpm  
I would agree with Aqua-regia. But when the test does work don't spill it on your hand!

Haha, after a frustrating waste of time playing with copper sulphate trying to dry what i thought was formic acid i stuck my finger in it and had a taste. Definitely extremely dilute.

Quote: Originally posted by unionised  

Calcium formate is a lot less soluble than calcium chloride.

Good idea problem is calcium hydroxide isn't soluble in alcohol. I'll see though. The reaction with sodium hydroxide was easy in fact if i had more then 5ml it would have overrun my condenser. Very exothermic.

aga - 20-12-2016 at 16:20

I recall blogfast25 telling me that it can easily be had from sodium formate, so i bought some, as it was cheap.

Never had a need for formic acid, so still have not looked up what he actually meant.

Best go do that now ...

Edit:-

Didn't take long : http://www.sciencemadness.org/smwiki/index.php/Formic_acid

Add sodium formate to <i>dilute</i> sulphuric acid and distill the formic acid off at 100-101 C. Conc H2SO4 just rips it apart to CO and H2O.

Alternatively, distill a pot of live ants like the discoverer, John Ray did in 1671. Ew. That's Ant-murder that is.

[Edited on 21-12-2016 by aga]

Glu0n - 21-12-2016 at 03:49

I did the oxalic/glycerol methol again, maintained 120c for 3 hours. Only had 20g oxalic acid left though. Ended up being too dilute, about 15ml of 20%. I reacted with ammonia, evaporated, then added 10ml 40% sulphuric acid and distilled. This was more like 50% Then dried with copper sulphate and distilled it out under vacuum. Final yield 1.7g lol. 8 hours work. I just ordered some off ebay from an awesome cheap Ukrainian seller so i will never have to do this again.

Ya Aga, distilling ants would disturb me. People pour molten aluminium down ant hills to make a casting too.

unionised - 21-12-2016 at 05:04

React chloroform with NaOH to get salt and sodium formate.
(I suspect that eaction works better if you add alcohol to get them to mix- if so, boil the mixture to get rid of alcohol)
Neutralise with HCl.
Add CaCl2 soln and evaporate down until much/ most of the Ca formate precipitates.
Filter it offf
wash it with alcohol (to get rid of the last of the CaCl2)
Treat Ca(HCOO)2 with dil H2SO4 to get dilute HCOOH
Filter off CaSO4 (or don't- it's a pig to filter, but if you don't it will clog up the distillation flask)
Distil the dilute acid to remove water + get the azeotrope.
Dry + redistil.

Metacelsus - 21-12-2016 at 08:24

Chloroform and alcoholic NaOH (or KOH) is a notoriously reactive mixture (it forms dichlorocarbene), so be careful.
Quote:

A chloroform-methanol mixture was put into a drum contaminated with sodium hydroxide. A vigorous reaction set in, and the drum exploded. Chloroform normally reacts slowly with sodium hydroxide owing to the insolubility of the latter. The presence of methanol (or other solubilizer) increases the rate of reaction by increasing the degree of contact between chloroform and alkali.


(https://webwiser.nlm.nih.gov/)

[Edited on 12-21-2016 by Metacelsus]