Question

Where can the solubility H table of formaldehyde in water at different temperatures be found?

Answer 1

Formaldehyde CH₂O one of the most important Intermediate product of the chemical industry. Because of its high reactivity, formaldehyde is mainly used in aqueous solutions, which often also contain methanol. In the solutions, the concentration of monomeric formaldehyde is low, as it reacts with water and methanol, forming oligomers, namely, polyoxymethylene glycol (HO(CH_{​​​​​ 2} O) _n H) in aqueous solutions and polyoxymethylene hemiformals ( H_{​​​​​​ 3} CO(CH ₂ O) _n H) in methanolic solution, respectively.

The equilibrium distribution of formaldehyde to the oligomer species depends on the overall formaldehyde and temperature. Even at moderate overall formaldehyde concentrations, substantial amounts of long-chain oligomers are formed. If a certain overall concentration of formaldehyde is exceeded, long-chain oligomers precipitate from the solutions. With increasing temperature, the solubility of the oligomers in water and methanol, respectively, increases and so does the overall formaldehyde solubility. It is well known that the formaldehyde solubility in aqueous solutions increases strongly if a comparatively small amount of methanol is added. This is in line with the fact that the average chain length of the formaldehyde oligomers in methanolic solutions is much smaller than it is in aqueous solutions. This suggests the following explanation for the stabilizing effect of methanol:

Formaldehyde, which was initially bound in long-chain, poorly soluble poly(oxymethylene)glycols, is transferred to short chain and therefore better soluble poly(oxymethylene) hemiformals. Another aspect is that methanol is a more favorable solvent for the formaldehyde oligomers than water. Typical technical formaldehyde solutions contain 0.30-0.50 g-g formaldehyde and 0.01-0.10 g-g1 methanol to stabilize solution and prevent solid precipitation.