An investigation of the reaction involving the preparation of hydrogen from sodium formate and sodium hydroxide;
HCOONa + NaOH = Na2CO3 + H2
This reaction is analogous to the two reactions involving the
preparation of methane and benzene from the sodium salts of acetic and
benzoic acids respectively;
CH3COONa + NaOH = NaCO3 + CH4
C6H5COONa. + NaOH= Na2CO3 + C6H6
Most of this investigation was experimental and I shall begin with an account of the experiments and the reactions involved.
Experiment I was a qualitative determination of the products of this
reaction. A mixture of the two substances was heated in a hard glass
test tube and the liberated gas was collected by water displacement
after being allowed to pass through a small bottle of distilled water.
In analysis the residue left in the test tube is referred to as the
solid, the small bottle of distilled water as the solution and the
liberated gas as the gas. The reactions which may have or did go along
wlth this reaction will be considered here;
(a} 2HCOONa = Na2CO3 + HCOH
This reaction is analogous to the preparation of acetone from sodium acetate; 2CH3COONa = CH3COCH3 + Na2CO3
(b) If formaldehyde were formed it would probably he reduced to methyl alcohol by the nascent hydrogen present;
HCOH + 2H = CH3OH
This reaction occurs readily in the presence of a catylist. e.g.
palladium or finely divided nickel. Neither formaldehyde nor methyl
alcohol was found to be present.
(c) 2HCOONa = H2 + (COONa)2
"When the alkali formates are heated away from air at 400° a good yield of oxalate is obtalned.”
(Organic Chemistry – Norris)
Both this and the two preceding reactions will be considered in the next
experiment. There was no sodium oxalate found in analysis which is to
be expected because an an excess of sodium hydroxide was used:
(d) (COONa)2 + 2NaOH = 2Na2CO3 + H2
This reaction which probably accompanies the reaction which forms sodium
oxalate (C) gives, of course, the same flnal result as the main
reaction. It will be considered in the third experiment.
(e) (COONa)2 = Na2CO3 + CO
This reaction is considered in experiment IV
Any carbon dioxide found would be formed probably from: 1. oxidation of
carbon monoxide 2. decomposition of sodium carbonate and 3.
decomposition after hydrolysis of sodium carbonate. None was found in
this experiment but it was found in later experiments.
Sodium carbonate and hydrogen were the chief products of this experiment; a small amount of carbon monoxide was found.
Experiment II was a consideration of the reactions which may have taken place when sodium formate was heated:
(a) 2HCOONa = H2 + (COONa)2
(b) 2HCOONa = Na2CO3 + HCOH
(c) HCOH + 2H = CH3OH
(d) HCOONa = NaOH + CO
(e) (COONa)2 = Na2CO3 + CO
(f) Na2CO3 = Na2O + CO2
All of these reactions have been considered with the exception of the
last. Sodium carbonate melts at 851° and decomposes before it boils.
This or the combustion of carbon monoxide (which occurs at 654° -
658°) or a partial hydrolysis and futher decomposition of sodium
carbonate should account for the carbon dioxide found in this
experiment. Sodium carbonate was found and only a very small amount of
formaldehyde was found in the solution as was proved when only the milk,
ferric chloride and sulphuric acid test for formaldehyde showed a
positive reaction, the other two being negative. ( see tests )
Hydrogen was the chief gas and a considerably higher percentage of
carbon monoxide was found in this than any other experiment. A high
percentage of sodium oxalate was found as was expected.
Experiment III was an account of the reaction:
(a) (COONa)2 + 2NaOH = 2Na2CO3 + H2
The two other reactions considered were:
(b) (COONa)2 = Na2CO3 + CO and
(c) Na2CO3 = Na2O + CO2
Only hydrogen and sodium carbonate were found.
No carbon monoxide, carbon dioxide, formaldehyde or sodium oxalate was
found in the tests. An excess of sodium hydroxide was used.
Experiment IV was a determination which involved this reaction:
(COONa)2 = Na2CO3 + CO
Sodium carbonate, sodium oxalate, carbon monoxide and carbon dioxide were found upon analysis.
No hydrogen, formaldehyde or methyl alcohol was found.
An experiment done along with this was the heating of sodium carbonate
which gave a small amount of carbon dioxide. I believe that this
was due to a decomposition after hydrolysis rather than before.
The final experiment is a summary of all the preceding research and of
the tests used throughout the analysis. A complete account of this
experiment follows:
EXPERIMENT V
HCOONa + NaOH = Na
2CO
3 + H
2
HCOONa: 5.1 g. used
NaOH: 3 g. used
Na
2CO
3: 7.95 g. calculated (7.79 g. actual)
H
2: 1.667 liters calculated (slightly more actual)
Carbon dioxide was not found in the gas before burning. (tested with Ca(CH)
2)
Carbon dioxide was found in very small quantities after ignition with a
hydrogen flame, showing the presence of small amounts of carbon
monoxide.
Hydrogen was by far the chief gaseous product.
Carbonic acid was not found in the solution.
The gas volume was slightly higher than calculated; the solid weight was .17 grams less than calculated.
The tests for formaldehyde were as follows:
(a) Fehlings solutions; (b) ammonium hydroxide so1ution of silver
nitrate (silver oxide); (c) milk, ferric chloride, and sulphuric acid.
All tests were negative.
The tests for methyl alcohol were:
(a) with a superficially oxidized hot copper copper wire
(b) with potassium permanganate. Both tests were negative.
The test for sodium carbonate was with hydrochloric acid and after the
carbon dioxide was liberated the solution was neutralized and the test
for oxalate was used. The test for the oxalate ion is based on the fact
that calcium oxalate is insoluble in water and acetic acid but soluble
in mineral acids- Sodium oxalate was found to be present.
The test for sodium formate was made: (a) by adding acid and mercuric
chloride which a formate would have reduced to the mercurous state, (b)
solidifying with concentrated sulphuric acid and heating, which would
have given carbon monoxide had a forrate been present. Neither test was
positive.
This last experiment shown that the reaction between sodium formate and
sodium hydroxide exists; that sodium carbonate and hydrogen are the
chief products,,and that the hydrogen is nearly pure.
SUMMARY
HCOONa + NaOH = Na
2CO
3 + H
2
( 2HCOONa = (COONa)
2 + H
2
(COONa)
2 + 2NaOH = 2Na
2CO
3 + H
2 )
HCOONa = NaOH + CO
(COONa)
2 = Na
2CO
3 + CO.
Na
2CO
3 + H
20 : 2NaOH + CO
2
2CO + O
2 = 2CO
2
2HCOONa = Na
2CO
3 + HCOH
HCOH + 2H = CH
3OH
TESTS
|
H2 |
Burning H2O formed |
Gas: |
CO2 |
Ca(OH)2 |
|
CO |
Ignition with H2 flame – Ca(OH)2 |
|
H2CO3 |
Acid |
Solution: |
HCOH
|
Fehlings sol.; NH4OH sol Ag2O; Milk, FeCl3, H2SO4 |
|
CH3OH |
Hot Cu wire; sol. KMnO4 |
|
Na2CO3 |
Acid |
Solid: |
(COONa)2 |
Add CaCl2 ppt. formed insol. H2O, CH3COOH; sol. HCl |
(residue)
|
HCOONa
|
Add acid and HgCl2 = HCOOH + HgCl2 = HgCl + 2HCl + CO2
Add conc. H2SO4 and heat = H2O + CO
|
COONa + NaOH = Na
2CO
3 + H
2
CH
3COONa + NaOH = Na
2CO
3 + CH
4
C
2H
5COONa + NaOH = Na
2CO
3 + C
2H
6
C
6H
5COONa + NaOH = Na
2CO
3 + C
6H
6
Completed
February 25, 1937
Reprinted here with permission from William Lipscomb. Unpublished, except on the Internet.