- Purification of Formaldehyde
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Commonly contains added MeOH. Addition of KOH soln (1 mole KOH: 100 moles (CAS NO. )) to 40% formaldehyde soln, or evaporation to dryness, gives paraformaldehyde polymer which, after washing with water, is dried in a vacuum desiccator over P2O5 or H2SO4. Formaldehyde is regenerated by heating the paraformaldehyde to 120 °C under vacuum, or by decomposing it with barium peroxide. The monomer, a gas, is passed through a glass-wool filter cooled to -48 °C in CaCl2/ice mixture to remove particles of polymer, then dried by passage over P2O5 and either condensed in a bulb immersed in liquid nitrogen or absorbed in ice-cold conductivity water.
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