Formalin: Methanol Oxidised over Silver

Formalin is formaldehyde dissolved in water. Methanol vapour and air pass over a silver catalyst at about 650 °C and turn to formaldehyde; the gas is taken up in water to about 37 %, with 10–12 % methanol left in to stop it polymerising. Formaldehyde is a known carcinogen, and a mouthful of the solution can kill. The picture: our diagram of reactor and absorber.