1636. Chaumat, H. Jan. 24, 1912, [Convention date]. Chrome alum, obtaining; electrodes.-In order to produce pure violet chrome alum, a solution of bichromate of potash and sulphuric acid is circulated through a cell containing a cathode which preferably consists of graphite or other powder rammed around a conductive core to form a porous cylinder. The anode, which may be made of, or cased with, platinum or gold, is placed in dilute sulphuric acid in a porous pot. If chromium compounds accumulate in the anode liquid, this is periodically transferred to the cathode compartment. The pressure may be 4À87 volts. Copper sulphate and other non-metallic substances, obtaining.-A soluble anode, consisting say of copper shavings and a copper conductor, may be used in the porous pot. The anode liquid is then circulated and kept at such a level that no chromium compounds diffuse into it.