The chemistry and kinetic behavior of Cu-Cr-As/B wood preservatives. III. Fixation of a Cr/As system on wood

The kinetic behavior of a Cr/As system in its reaction with wood is described, as are its reactions with lignin and carbohydrates of wood for Cr^VI alone. Chromium^III arsenate complexes with the guaiacyl units of lignin, as well as the usual chromic acid/guaiacyl unit complexes already characterized, was formed. The interference of As concentration on the various zones of fixation of chromium are identified. Complexes between guaiacol and chromium arsenates indicate that in this Cr/As system Cr^III can also be linked to the guaiacyl units of lignin when in the form of CrAsO₄·6H₂O contrary to what obtained with systems not containing As. An initial increase in the rate of reduction Cr^VI → Cr^III by the carbohydrates fraction in wood is ascribed to the catalytic effect of the arsenic. The percentages of chromium fixed onto lignin and cellulose of wood compare well with experimental values.