Bayer poisons : degradation of angiosperm and gymnosperm water-soluble extracts in sodium hydroxide at 145� C

In the Bayer process of preparing alumina from bauxite small molecular weight compounds such as C2-C6, mono-, di-, and trialiphatic carboxylic acids which have hydroxy substituents are formed from a humic material. While involatile as anions under refinery conditions, upon acidification they become volatile and can be lost either in processing or in workup of process liquors in the laboratory. The origin of these organics is unknown; however, this paper shows that they are directly derived from the water-soluble (mainly carbohydrate) fraction in the vegetation that is dissolved with the bauxite in preparing process liquors. Glucitol is shown to be a particularly stable carbohydrate to digestion and may, therefore, play an important role in Bayer poisoning processes.