Abstract: A method of treating a ballast water for sterilizing bacteria, microorganisms or organisms in the ballast water in a hold or ballast tank of a ship, has the steps of: sterilizing the bacteria, microorganisms or organisms by adjusting a residual chlorine concentration in the ballast water to 1 mass ppm or more and 1000 mass ppm or less with a hypochlorite, and removing the residual chlorine in the ballast water with a sulfite.

Abstract: Disclosed is an apparatus for supplying hydrogen chloride gas from a hydrogen chloride gas generator to an absorbing reactor through a gas supply pipe, and a method for producing hydrochloric acid by allowing the gas absorbed in water in an absorbing reactor. The apparatus obtains a large amount of high purity hydrochloric acid having extremely low impurity concentration with a simple system. The inner wall of the gas supply pipe is constructed with such materials from which impurities are not eluted by hydrochloric acid at least to the position of the wall which is reached by the backward flow or splash of produced hydrochloric acid, vapor of the hydrochloric acid or water in an absorbing reactor.