motrin
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Formic acid, manufacture/procurement
WOW, I'm afraid of hydrocyanic acid (not that I'd know where to get it!
and I'm also a tad leery of 40 atm.
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BromicAcid
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Fractional distillation of red ants 
Although you could oxidize methanol with dichromate or permanganate. Any organic chemists want to give help on a procedure? Or you could take a salt
like sodium formate and treat it with H2SO4 of a suitable dilution and distill. Or maybe Ca(OOCH)2 and H2SO4, usually precipitates made in this
manner are hard to filter, but not always, look at the wet manufacture of phosphate fertilizers.
I know that in some areas of the world it is sold over the counter in high concenrations, for descaling or something of that nature, it's
slipping my mind at the moment.
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Geomancer
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Aqueous formic acid can be obtained by heating oxalic acid in glycerol; see Rhodium's page. Fractional destructive distallation of oxalic acid
might work. Formates+H<sub>2</sub>SO<sub>4</sub> can also be used. CO may be evolved? Formates may be prepared with the
corresponding hydroxide and CO containing gas. If someone knows the details please post.
Rhodium also gives a preparation using lead formate and H<sub>2</sub>S. I think I'd stay away from that.
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motrin
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Frac. Dist. Of R.A. :D
| Quote: | Originally posted by Geomancer
Formates may be prepared with the corresponding hydroxide and CO containing gas. If someone knows the details please post.
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| Quote: | Originally posted by Geomancer
Formates may be prepared with the corresponding hydroxide and CO containing gas. If someone knows the details please post.
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When methanol and carbon monoxide are combined in the presence of a strong base, the formic acid derivative methyl formate results, according to the
chemical equation
CH<sub>3</sub>OH + CO → HCOOCH<sub>3</sub>
Industrially, this reaction is performed in the liquid phase at elevated pressure. Typical reaction conditions are 80°C and 40 atm. The most widely
used base is sodium methoxide. Hydrolysis of the methyl formate produces formic acid:
HCOOCH<sub>3</sub> + H<sub>2</sub>O → HCOOH + CH<sub>3</sub>OH
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BromicAcid
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Although a bit of a waste in my opinion one exotic method goes along the lines of the following:
4KOH + CHCl3 ----> HCOOK + 3KCl + 2H2O
Although the reaction is somewhat violent I would guess. And I don't recall if it's run in aqueous conditions or with solid KOH.
Then the potassium formate can be added to 6M H2SO4 and the azetrope distilled.
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Organikum
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Electrolytic:
By venting CO2 into the cathode chamber of an electrolytic cell electrlolysing water.
I have seen a patent on this - will try to find it again.
or:
From Hexamine/HCl or (para)formaldehyde/HCl-catalytic and alcohol.
The ethylformate (methylformate if MeOH is used) formed dissoziates in water, so adding lots of water to the formate should enable one to distill away
the alcohol and have a water/formic mixture leftover which can be concentrated by the usual ways.
[Edited on 2-4-2004 by Organikum]
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t_Pyro
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Performing the haloform reaction with ethanol will result in a solution of sodium formate in the aqueous layer. The sodium formate can be treated with
dil. HCl to get pure formic acid.
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unionised
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Here in the UK you can get it OTC as "ataka"; a descaler. That gives you 40% w/w. I guess you can distill it if you need a higher
concentration but the Bpt is very close to water so that migt not work well.
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Marvin
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Geo,
6 to 8 atmospheres, 120 to 150C, quantitive yeild.
I thought Id posted the method before, and that if you had KOH, or a mixture of KOH and NaOH that it would go with 1 atmosphere, though I cant find it
and so this modification is suspect.
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Organikum
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BASF posted the details on the CO + NaOH at 8 atm somewhere here as I remember.
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Dave Angel
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Re: Ataka
With some formate esters in mind, I've spent the day attempting to use my fractionating column to distil Ataka descaler as was suggested by
unionised. My column is 24/29 250mm packed with chunks of broken pyrex (5-7mm per side).
I heated 500 ml of neat Ataka SG 1.096 in a 1L rb flask and after a few hours collecting fractions got the following results
| Code: | Fraction Volume/ml SG
1 197 1.056
2 108 1.080
3 37 1.096
4 43 1.118
5 32 1.132
6 36 1.148
7 29 ~1.16 |
The last SG reading is an approximation as it went off the scale of my hydrometer (a standard brewing type).
It's really not that easy getting good separation of water and the high boiling azeotrope as they have such close boiling points and my column
isn't ideal. Having said that, I got 177 ml of formic acid equal to or greater than 40% out of it, which I plan to dry further. The remaining
acid could be converted to the sodium salt for making more concentrated formic acid with dilute H2SO4 as described here, or for experiment as polverone suggested in the NaHSO4 thread.
I'm not quite sure what to do with regards to the drying. My current plan is to use plenty of boric anhydride, which may not be suitable for
drying until the acid is already much more concentrated - anhydrous copper sulphate being another option, but again it is listed for use when the acid
is at 88%.
It may well prove more economical to prepare formic acid from a salt and H2SO4 or NaHSO4 - in fact it's probably more economical just to buy a
litre of 98%, but it's always more satisfying to get it OTC. 
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chloric1
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if you have 88% formic acid would anhydrous calcium chloride convert it to the anhydrous acid. Did I find this from rhodium? I cannot remember.
Fellow molecular manipulator
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Dave Angel
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The link I gave indicates that CaCl2 is unsuitable for dehydration of formic acid, which is a shame given that it is readily available to be used
immediately, w/o the dehydration step copper or magnesium sulphate requires. Copper sulphate is looking like a more suitable drying agent now, and
that would be less wasteful of boric anhydride should that method fail - though I may still run some tests on a small sample.
From a few rough calculations it seems that specific gravity and percentage composition of formic acid have a non-linear relationship. I may have to
work out a suitable titration, but if someone else already knows the end point for a formic acid / NaOH titration and suitable indicator then do say!
I'll just need to sort out some standard NaOH.
[edit] Now I think about it, phenolphthalein should be suitable for a weak acid / strong base titration such as this.
[Edited on 3/26/2005 by Dave Angel]
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S.C. Wack
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Lorin wrote a very long time ago in Bull. soc. chim., Compt. rend., and Ann. chim. phys. of the reactions and preparation of formic acid in several
articles, but for some reason his dehydration of hot 70% acid with dry oxalic acid doesn't get mentioned much these days. The dihydrate
crystallizes out, leaving a fairly dry acid which can be distilled and crystallized. Nor his use of glycerin in the usual way but with the dry oxalic
and and at a lower temperature, to obtain an acid rather stronger than the one gets from the dihydrate. I wonder why, because he also worked out the
details of the usual method from the dihydrate, which has become widely printed.
There is a patent on the bisulfate/formate method: DE 193509
It is CuSO4/distillation that is used on the 88% acid.
And here is an old CRC sp. gr. table for formic acid.
Attachment: formic_spgr.pdf (40kB)
This file has been downloaded 817 times
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Dave Angel
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Thanks for posting that table; it sounds really useful, but I'm having a hard time downloading it - not sure if it's my end or the other,
but it keeps counting up despite an incomplete download!
Anyone else having problems?
[edit] No worries, I finally managed to get it to download, but it took something like 5-6 minutes after hanging at 99%! Thanks again S.C. Wack,
that's the perfect table for the job.
[Edited on 3/26/2005 by Dave Angel]
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