Concentration of Formic Acid

[potisgood]

Does anyone know what the maximum concentration of water in the performic mixture is that will not greatly interfere with methyl man's performic procedure?  (If the H2O2 is 27%, how concentrated must the formic acid be?)

[Rhodium]

As long as you have at least 70% formic acid yuo should do fine. Be sure to adjust the amounts of formic acid and hydrogen peroxide to account for your lower concentration (so that you have the same number of moles of HCOOH and H2O2).

http://rhodium.lycaeum.org

[firecracker]

Rhodium (et al),

Some questions:

1) If you have a lower concentration of formic, distillation of the excess water at 100C, followed by distillation of the azeotrope should yield 77% formic (bp107C), correct?  The literature talks about vac distillation, but isn't that is only for higher concentrations?  Formic acid thermal decomposition occurs at 160C,  and I thought I remember a BASF document that stated that 85% formic exposed to atmosphere would only degrade a few percentages over a couple of months.  This would indicate (to me) that simple distillation should be fine for 77%.

2) Assuming you wanted higher concentration (why?), does anyone have any idea of how much more water copper sulfate would draw out of the solution? I would imagine it would be around 85%, but thats just a guess.

Thanks,
fc

Snap, Crackle, Pop

[baalchemist]

Fractional crystallization works on formic,requires some skill & patience.

Godisnowhere.

[firecracker]

baal,

Thanks for the input. I do realize that crystallization would work, but my question is why would you do it?  For dilute concentrations of formic, wouldnt simple distillation provide what you need?

fc

Snap, Crackle, Pop

[baalchemist]

Sure it would work for that purpose, but seperating water from formic via distillation wont happen.
H2O=bp 100c    Formic= bp 100.7c

Godisnowhere.

[WonderWoman2001]

Yes but does the 'azetrope' of water and formic not take a higher bp? Allowing distillation to work in concentrating to around 70%. as baalchemist states......


If you have a lower concentration of formic, distillation of the excess water at 100C, followed by distillation of the azeotrope should yield 77% formic (bp107C), correct? 



What's the final answer on this, who's dreamed it!!

WW

[WonderWoman2001]

sorry..... I mean't firecracker.

WW