Process for the electrochemical production of ammonium polysulfide

A process of producing ammonium polysulfide (APS) in at least one electrochemical cell, said electrochemical cell comprising:

• (a) an anode;
• (b) a gas diffusion cathode comprising an electrically conductive, gas-permeable carbon layer;
• and
• (c) an electrolyte chamber between said anode and said gas diffusion cathode;
• wherein:
• said anode and said cathode are directly or indirectly connected to a source of direct electric current outside of said electrochemical cell so that a cell voltage of 0.01 to 5V results within said electrochemical cell;
• said electrolyte chamber is supplied with an electrolyte comprising an aqueous ammonium sulfide solution;
• a gas containing free oxygen and said electrolyte are able to flow between said anode and said cathode;
• and
• said anode and said cathode are in contact with said electrolyte;
• said process comprising:
• (i) feeding a gas containing free oxygen over said carbon layer into the electrolyte chamber and into contact with said anode;
• (ii) forming hydroperoxide anions (OOH.sup.-) and APS in said electrolyte chamber;
• and
• (iii) withdrawing from said electrolyte chamber a solution comprising APS and a residual gas;
• wherein at least 10 percent by weight of the APS which is formed is generated by the gaseous free oxygen which is introduced into the electrolyte chamber.