Oxalic Acid: Wood Soaked in Caustic Alkali and Heated in Hot Air at 300 °C (Plater-Syberg)

Oxalic acid from wood by Plater-Syberg's process (English Patent 23682, 1893), as Thorpe's Dictionary (1913) gives it: wood soaked in caustic alkali is heated in hot air. At about 120 °C it gives mostly acetic acid; at about 300 °C with more air, almost only oxalate. The oxalate is turned into calcium oxalate, which sulphuric acid breaks up to oxalic acid. Hot caustic and strong acid burn: goggles, gloves. The picture: our diagram.