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Author: Subject: Does ammonium formate sublime?
beastmaster
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[*] posted on 16-7-2008 at 23:11
Does ammonium formate sublime?


I needed 2 grams of ammonium formate. I couldn't find much info on preparation, but it seemed pretty straight forward. I generated my NH3 with ammonium sulfate from home depot and NaOH. Of course everything leaked but I learned. Bubbling the NH3 into chilled HCOOH(manually stirring) I bubbled for hours checking the PH. It never did get netrual, but my hose did start filling up with the formate and I was able to get some beautiful crystalls on recrystallization and soon had my two grams. It melted after I left it out on a plate, but a min. in the microwave brought it back. Several hours later I again microwave the puddle to bring it back, but this time I was left with a 1/4 gram. Does this stuff sublime. It really pissed me off as i had to go back to being gassed and fill my hose again with formate.What happened? I have more desire them knowledge. Any help on this problem is appreciated . Thank you
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Rosco Bodine
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[*] posted on 16-7-2008 at 23:34


Get it hot enough ~160C IIRC and it decomposes to
formamide, get the formamide vapors very much hotter
still and you get cyanide.

BTW you can neutralize formic acid with a slow drip of
ammonium hydroxide, but it generates a lot of heat,
use a flask no more than about a quarter full of the formic
acid at the start and go slowly drop by hissing drop with good stirring. It will reach the B.P. if you are doing much of it
like a half liter at any decent rate.

[Edited on 17-7-2008 by Rosco Bodine]
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[*] posted on 17-7-2008 at 03:13


Preparation of ammonium formate is desribed (for example) here:
http://dx.doi.org/10.1021/ja01440a010
If you cannot obtain neutral pH, it is very probable that you have made an acid ammonium formate. Solution after saturation with NH3 should possess strong ammonia smell. Melting point of pure HCOONH4 is 117 C.
According to literature, this salt can be sublimated without decomposition below 100 C under reduced pressure (<20 mm Hg).
My crystalline ammonium formate (from 80% formic acid and NH3aq) does not change itself in microwave oven (360 W, 2 minutes) and mass stays the same.
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[*] posted on 17-7-2008 at 10:11


Ammonium formate is deliquescent and pretty soluble in water.
Thus leaving it out in the open air will cause it to quickly form a strong solution of the salt.

It is also the product of a weakish base and a strongish acid, hence solutions of it will tend to be acid except in the presence of excess base.

I would suggest adding strong ammonia solution to cooled formic acid and vacuum filtering off the precipitated salt after vacuum concentration if required.
Transfer the product to a weighed jar and dry in a vacuum dessicator to constant weight.
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[*] posted on 17-7-2008 at 11:30


I've also had a similar problem, by slowly evaporating an amm. formate solution from 28% NH3 and 75% HCOOH, loosing quite some product even though the temp hardly went over 100°C at first, then lower as most of the water was gone.

Flush the viscous liquid with acetone to get the crystals insteaed of waiting for it to form a solid.




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[*] posted on 17-7-2008 at 13:51


No smell of ammonia or formic acid during the losses???

You may find it more convenient to use ammonia in the form of a solid salt in making the formate, and acetate, even if it foams much.
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[*] posted on 18-7-2008 at 00:44


Quote:
Originally posted by Rosco Bodine
Get it hot enough ~160C IIRC and it decomposes to
formamide, get the formamide vapors very much hotter
still and you get cyanide.
[Edited on 17-7-2008 by Rosco Bodine]


Cyanide is not very stable when hot...being endothermic from its elements...cyanide is explosive...Cases have been seen where pure HCN did selfpolymerise at STP after monthes in the original drum leading to selfheating and explosion.
H-C#N just like HC#CH and N#C-C#N are detonable.
To be remembered HCN burns with a flame heat of >3500°C.




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[*] posted on 18-7-2008 at 00:48


Quote:
Originally posted by Klute
Flush the viscous liquid with acetone to get the crystals insteaed of waiting for it to form a solid.


Better use methanol or ethanol (eventuelly with the help of diethylether) than aceton for that purpose.
Aceton reacts with NH3 and with acidic media to lead to crotonisation products...so only use when fast removed from the cristals...




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[*] posted on 18-7-2008 at 14:04


i buy my ammonium formate from my local hardware shop as grease preventer (62% ammonium formate , the stuff doesnt work lol).
I evaporate the soloutioin and i eventually get a dry white solid that smells quite a lot off ammonia.
After hours of research into the substance (thats how cool i am lol:P i found out this,

'Industrially ammonium formate is prepared from saturated ammonia soloution and conc. formic acid in a water cooled vessel. Ammonium formate, NH4HCO2, is not prepared in industry via ammonia gas as the reaction produces ammonium formate with a sponge structure wich eventually leads to molecules of water and formic acid being trapped in the structure.'

this would definatly explain why you couldnt get a neutral soloution easily and the loss in mass after heating (microwave)

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[*] posted on 19-7-2008 at 10:38


Thank you all for taking the time to reply to my question. I was aware that the formate could change to CN at high temp. I thought that this may be a route to naCN at a later time, but after gassing my self while generating NH3 I think I'll stay away from HCN, SO3, and other lethal gases,and subsistences tell I get a lot more experience. I think My next attempt to make the NH4formate I'll try using NH3OH, and drip it slowly into the formic acid. Now if I can just figure out how to set up a drip,and build me a magnetic stirrer. Thanks again.
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[*] posted on 7-2-2012 at 18:15


Quote: Originally posted by ScienceSquirrel  
Ammonium formate is deliquescent and pretty soluble in water.
Thus leaving it out in the open air will cause it to quickly form a strong solution of the salt.

It is also the product of a weakish base and a strongish acid, hence solutions of it will tend to be acid except in the presence of excess base.

I would suggest adding strong ammonia solution to cooled formic acid and vacuum filtering off the precipitated salt after vacuum concentration if required.
Transfer the product to a weighed jar and dry in a vacuum dessicator to constant weight.

How about listing where it is free James Kendall, Howard Adler
J. Am. Chem. Soc., 1921, 43 (7), pp 1470–1481:cool:
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[*] posted on 11-2-2012 at 20:39


Interestingly, per my recent readings, I happen to come across the Tollens' Reagents test. It occurred to me that theoretically for someone with access to Silver (which may be recycled in this reaction), this is a possible path for the home chemists to Ammonium formate, NH4HCO2. The Tollens' reagent test in general is for any aldehyde, RCOH:

RCOH + 2 Ag2(NH3)2OH ---> 2 Ag(s) + NH4(+)RCO2(-) + H2O + 3 NH3

which, in our case of interest, taking R is a single hydrogen (H), the synthesis would be based on formaldehyde, H2CO, and Tollens' Reagent.

LINK (Please complete the link by pasting the last part > (Classification_Tests).pdf ):
http://opencourseware.kfupm.edu.sa/colleges/cs/chem/chem303/... (Classification_Tests).pdf

Note, the Silver is deposited as a mirror on the glass vessel. Upon pouring out the solution and drying (or crystallization after heating the solution), one may theoretically obtain Ammonium formate.

I have dissolved solid Silver slowly in dilute Acetic acid/H2O2 solution. This forms Silver acetate which remains soluble in the vinegar solution, but upon neutralizing with NaOH or NH4OH, a white curd of Silver acetate forms. Separate out the Silver acetate, wash and then further reduce with a base to insoluble Ag2O (brown/black). Add NH4OH to dissolve the Ag2O and create Diamminesilver(I) hydroxide, Ag2(NH3)2OH. Note, avoid storing the Tollens' Reagents solution, especially after applying heat or sunlight as this may result in time with the formation of the dangerous (explosive even in solution) Silver Nitride, Ag3N, so called Fulminating silver. For the record, I have never gone the extra step of adding formaldehyde to Tollens' Reagent in an attempt to create Ammonium formate. However, here is an account (source: "Organic Chemistry Microscience Experiments Teaching and Learning Materials", page 19):

"Part 2.1: Reduction of Ammoniacal Silver Nitrate Solution - Tollen&#146;s Test

When preparing the &#147;Tollen&#146;s reagent&#148; in the large wells of the comboplate®, brown silver oxide (Ag2O(s)) is formed by adding sodium hydroxide solution to the aqueous silver nitrate. This precipitate must be dissolved with the ammonia so that [Ag(NH3)2]+ ions can be formed in solution. An excess of ammonia must be avoided, therefore the ammonia solution must be added dropwise with stirring. Sometimes it may appear that the silver oxide has not completely dissolved, but if stirring is continued for a short while all the small, brown particles of silver oxide will eventually be dissolved. No more than 25 drops of 1 M NH3(aq) should be added. The number of drops of aldehyde added to the reagent varies between 1 and 3, depending on the aldehyde used. Only one drop of formaldehyde is required to form a conspicuous silver mirror. The silver mirror formed with butyraldehyde is however not as evident when one drop of the aldehyde is used. Three drops of this aldehyde is preferable if a better silver mirror is desired. A waiting period of five to ten minutes is required to allow the silver recipitate to accumulate on the bottom and sides of the well. Formaldehyde reacts immediately and the silver mirror is normally detected before five minutes has lapsed. Other aldehydes, like butyraldehyde, react more slowly and the silver is only evident after some time. If another aldehyde is used by the teacher and a silver mirror is not observed after 10 minutes, the comboplate® should be floated in a container of warm - but not boiling - water (approximately 350C). A silver mirror should form within a few minutes.
The appearance of the silver mirror varies with the aldehyde used. For example, the mirror formed with formaldehyde is very shiny whereas that formed with butyraldehyde is somewhat darker. It is usually necessary to tilt the comboplate® towards the light to show the silver deposit on
the sides of the wells.
The silver solutions should never be heated excessively, nor left to stand unnecessarily since explosive silver fulminate may be formed. Once the experiment has been completed, the residue from each well must be thoroughly rinsed way. Dilute nitric acid must then be added to each well to remove any silver mirror and prevent the formation of fulminates. Sometimes there is still some black residue that remains in each well after washing with nitric acid. This can be removed with a cotton bud or wooden skewer as previously described"

LINK:
http://unesdoc.unesco.org/images/0015/001508/150840E.pdf

As a sidebar, I believe factors not always stress in driving the creation of Ag3N is heat (from water baths or possibly sunlight) given the large endothermic heat of formation of Ag3N (see thread cited below), and secondly, loss of water (or elevation in pH) based on the chemistry seldom examined:

1. Ag2O(s) + 4NH3 (g) + 4H2O <---> 2 [Ag(NH3)2]OH + 3H2O [1]

Note, I have written this reaction as reversible (see as a source, "Second year college chemistry" by William Henry Chapin, page 255):

"As might be expected, the silver-ammonium complex dissociates slightly into its constituents as indicated by the equation

Ag(NH3)2+ <==> Ag+ + 2 NH3 [2]

This is a reversible reaction, very much like the ionization of a very weak acid or base." I suspect that by making the environment less prone for the retention of NH3 (for example, by applying heat or adding NaOH or alcohol to remove water) would move equation [2] to the right, that is, reversing equation [1]. Continuing the point, an equation for the creation of Silver Nitride can be written for one mole of Ag2O as:

2/3 NH4OH (aq) + Ag2O (s) --> 2/3 Ag3N (s) + 5/3 H2O [3]

which interestingly implies that less NH3 is required to form the Silver nitride than the Diamminesilver(I) hydroxide and, to my point, removing water drives equation [3] to the right. Also, one could argue, when there is a stoichiometric excess of either NH3 (hence, the ammonia concentration argument) or Ag2O, and sufficient heat, then equation [3] moves to the right and forms Silver nitride.

Some supportive references: Per The WiZard is In - 7-6-2010, Link: http://www.sciencemadness.org/talk/viewthread.php?action=pri...

"These observations tally to a great extent with those of the present author. As far as his experiences go, over a period of thirty-five years, there was never an explosion from fulminating silver when silver nitrate and ammonia alone were mixed, independent of their strength. He has, however, read that such explosions occurred when the mixture was heated on a water bath.

But fulminating silver was formed and explosions took place when strong alkali hydroxides were present, or when the solution became concentrated through evaporation. A similar conclusion was reached by the Pittsburgh Plate Glass Co. of U.S.A. in 1955, i.e. that:

(1) Explosions are not produced by adding concentrated ammonium hydroxide (ammonia) to solid silver nitrate.
(2) Addition of sodium or potassium hydroxide to the silver-ammonia complex definitely increases the tendency to form explosive material. The action of the alkali hydroxides is not quite clear, but may be explained by their tendency to displace ammonia.
(3) A very high alkalinity of pH 15 appears to favour formation of explosive. The pH of usual silvering solutions is about 13-4. The dangerous pH region starts at about 14-5.
(4) Although the concentrated silver-ammonia complex appears not to form fulminating silver, it is recommended to dissolve silver nitrate in water before adding ammonia.
(5) Therefore, silvering solutions should not be stored, and under no circumstances over longer periods such as weekends."


[Edited on 12-2-2012 by AJKOER]
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[*] posted on 12-2-2012 at 07:30


The more dilute the solution is, the greater the loss of ammonia in isolation. It is a free spirit, nonconformist, light, weak, and unpopular but free, free....

I still think that even if you have to make the formic acid old school, carbonated ammonia is most convenient for actually isolating the salts.




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[*] posted on 12-2-2012 at 08:51


By far the easiest ammonium formate synthesis is to buy ammonium carbonate (see above answer) (bakery supply co. or e-bay), then buy HCOOH on e-bay.

Add 1.03 equiv. of formic acid slowly. Wait for gas generation to cease. Reduce vol. by distillation, place in ice-bath --> crystalline ammonium formate.

[Edited on 12-2-2012 by Zan Divine]
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[*] posted on 6-2-2014 at 07:09


Can ammonium bicarbonate be used to synthesize ammonium formate in the above manner?

[Edited on 6-2-2014 by GoldGuy]
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[*] posted on 6-2-2014 at 08:31


Quote: Originally posted by GoldGuy  
Can ammonium bicarbonate be used to synthesize ammonium formate in the above manner?

[Edited on 6-2-2014 by GoldGuy]


You can try to prepare aqueous (NH4)2CO3. My untested suggestion for the home chemist (I may test this approach in the near future): react aqueous ammonia in excess with basic magnesium carbonate in a closed container between 33 C and 50 C:

2 NH3 + H2O + MgCO3.Mg(OH)2.3H2O (s) --> 2 Mg(OH)2 (s) + (NH4)2CO3 + 2 H2O

The reaction is expected to work becomes even it does result in only CO2 formation and not the salt, in the closed vessel with increased pressure, the CO2 and aqueous ammonia will form the ammonium carbonate per the commercial process (see, for example, Patent 1,909,757 at http://www.google.com/patents/US1909757 and click on 'images' for the more readable pdf version).

Note, the action of Na2CO3 on warm aqueous MgSO4 rapidly forms the insoluble basic magnesium carbonate (see, for example, page 317 at http://books.google.com/books?pg=PA317&lpg=PA317&dq=... ).

[Edited on 6-2-2014 by AJKOER]
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[*] posted on 6-2-2014 at 14:29


You can just bubble CO2 thru the solution
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