Formaldehyde

Formaldehyde is supplied as a 37-40% w/v (12.3 M) solution that may contain a stabilizer such as methanol (10-15%). Formaldehyde oxidizes readily to formic acid when exposed to air. If the pH of the formaldehyde solution is acidic (<pH 4.0) or if the solution is yellow, the stock solution should be deionized by treatment with a mixed bed resin, such as Bio-Rad AG-501-X8 or Dowex XG8 before use.