Oxalic acid at 100 ℃ start sublimation , when rapid sublimation 125 ℃ , 157 ℃ when a large number of sublimation , and begin to decompose.
With a base , may occur esterification, acid halide , an amidation reaction . Reduction reaction can also occur , heat decarboxylation reaction . Anhydrous oxalic acid is hygroscopic . Oxalic acid can dissolve in water to form complexes with many metals .
Acidity
Oxalic acid than acetic acid ( acetic acid ) 10000- X , the acid is an organic acid . Its an ionization constant Ka1 = 5.9 × 10 ^ -2, two ionization constant Ka2 = 6.4 × 10 ^ -5. With continuity acids. Can occur with alkali neutralization, the indicator can change color , can emit carbon dioxide and carbonate role .
For example : H2C2O4 + Na2CO3 == Na2C2O4 + CO2 ↑ + H2O
H2C2O4 + Zn == ZnC2O4 + H2 ↑
Reductive
Oxalate has a strong reduction, and oxidant easily oxidized into carbon dioxide and water [ 1 ] . Can make acidic potassium permanganate (KMnO4) solution fade, and reduced to divalent manganese ions. This reaction is used as a quantitative analysis method for determining the concentration of potassium permanganate . Oxalic acid can also wash away spilled ink on the cloth track .
2KMnO4 +5 H2C2O4 +3 H2SO4 == K2SO4 +2 MnSO4 +10 CO2 ↑ +8 H2O
H2C2O4 + NaClO == NaCl +2 CO2 ↑ + H2O
Instability
Oxalic acid at 189.5 ℃ or in case of concentrated sulfuric acid will decompose to produce carbon dioxide , carbon monoxide and water.
H2C2O4 ==== CO2 ↑ + CO ↑ + H2O
Laboratories can use this reaction to the admission of carbon monoxide gas .
Hydrogen oxalate to carbon dioxide, carbon monoxide, ammonia , and water 200 degrees
Toxicity
Oxalic acid is poisonous. On the skin , mucous membrane irritation and corrosion, easily through the skin , mucous membranes absorb lead poisoning . Air maximum allowable concentration of 1m g/m3.
Esterification
Acetic acid ester with an alcohol can be generated . For example, the reaction of acetic acid with ethanol, ethylene malonate.