To adjust pH without changing components of a solution.
This pH adjusting device 1 is equipped with a gas feeding device 4 which injects the solution 2 and gas such as a nitrogen gas having no chemical reaction on gaseous component dissolved in the solution 2 into the solution 12, and a pH measuring instrument 5 which measures the pH of the solution 2 The gas feeding device 4 controls the amount of the injected gas according to the measured value of the pH measuring instrument 5. The pH measuring instrument 5 measures the pH in the solution 2 and sends its measured value to a controller 4-3 in the gas admitting device 4. The pH adjusting device 1 controls the amount of the gas injected into the solution according to the pH measured value. Consequently, the gas dissolved in the solution is discharged and the hydrogen ion concentrtion 'H*' in the solution is varied too adjust the pH of the solution, to a specific pH value.
NARA MASAYUKI
ARATA YOJI
