Chromic acid, electrochemical regeneration

Maintenance of chromium plating baths causes ecological problems that can be solved by electrochemical methods, especially by using membrane electrolysers (i.e. electrodialysis) [39-41]. In these processes, chromium(III) is oxidized at the anode, usually made of lead, to chromium(VI), whereby chromic acid is regenerated. The chromic acid consumed in the plating process is then replaced by adding CrO in the solid form. 

Since 1927 chromic acid has been used for the oxidative bleaching of Montan waxes. Hoechst has been operating the electrochemical regeneration of chromic acid for more than 90 years. The newly developed electrochemical process (as enlargement and partial replacement for the existing plant) is based on the... 

The oxidation of naphthalene was carried out with chromic acid and chromates, regenerated by electrochemical reoxidation. This method was first used by the Farbwerke Hoechst. In 1891, it was accidentally discovered at BASF haX naphthalene could be oxidized by concentrated sulfuric add in the presence of mercury. In 1897, introduced the first synthetic indigo to the market, followed shortly thereafter by Farbwerke Hoechst, Synthetic indigo rapidly replaced the natural product in the market in spite of harsh competition of the producers of natural indigo, especially of the Provence/France. 

---