Recently, the seawater hydrogen ion concentration index (pH) method developed by the Honorary Fellows of the Japan Industrial Technology Research Institute (Institute of Industrial Research), the researcher of the research on the seawater hydrogen ion concentration (pH), has been recognized by the International Organization for Standardization (ISO). And become an international standard. This standard is used to monitor carbon dioxide for leaks and leaks when storing carbon dioxide in a submarine aquifer.

The Japanese marine research and development agency and the environmental TECHNOS company (THE GENERAL ENVIRONMENTAL TECHNOS Co., LTD) developed specific testing techniques. The researchers first sealed the seawater in the glass unit of the spectrophotometer and measured the absorbance when the beam of specific wavelength was illuminated. The pH value of the seawater to be measured is determined by adding a color change indicating the cresyl violet between the drugs, and thereby the relationship between the seawater absorbance and the pH value is established. Since the pH value of seawater generally varies between 7.3 and 8.3, and the cresol purple in the indicated drug has a large chromatic aberration change in this range, the high-precision pH value can be grasped by the absorbance measurement method.