Abstract: The efficiency of the Solvay chlorine dioxide producing process is enhanced by the use of a high total acid normality and a single vessel generator-evaporator-crystallizer.

Abstract: Chlorine dioxide is produced in a continuous process by reaction of sodium chlorate and hydrochloric acid. The reaction medium is maintained at its boiling point under subatmospheric pressure and the resulting steam is used to dilute the chlorine dioxide and chlorine and remove the same from the reaction zone. Sodium chloride is deposited from the reaction medium in the reaction zone. The mole ratio of chlorate to chloride in the reaction medium, and the temperature of the reaction medium are controlled within narrow limits to provide high efficiency of production of chlorine dioxide.

Abstract: An electrode having a conductive platinum alloy coating and which has deteriorated in use in an electrolytic chlorate cell is heat treated at elevated temperatures of above 300.degree. C to regenerate the coating. The regeneration of the coating is exhibited by a decreased oxygen concentration in the cell off gases after the heat treatment. Further improvement in cell characteristics in severely deteriorated anodes may be achieved by coating the anode surface with a platinum group metal prior to or during the heat treatment.

Abstract: A chlorine dioxide-producing process is provided in which water vapor is used to dilute and remove the chlorine dioxide produced from sodium chlorate and hydrochloric acid from the reaction vessel. A cyclic arrangement is provided in which the recycle liquid heated to the boiling point of the reaction medium in the generator is allowed to expand gradually to provide a vapor/liquid/solid mixture which is discharged at low velocity to the generator. Vibration due to boiling is considerably reduced and wear of generator walls due to impinging materials is eliminated.

Abstract: Elemental phosphorus in electrothermal phosphorus plant effluents is oxidized either by anodically produced atomic oxygen or by an anodically produced mixture of atomic chlorine and atomic oxygen. The elemental phosphorus content of the effluents may be lowered by use of this process from about 5 to 10 ppb to an undetectable level, i.e., below about 0.1 ppb.