As the basic research for the study of mechanism of ventilation in submerged fer mentations, the formula of carbon dioxide in the liquid phase was investigated. Carbon dioxide in liquid phase was mainly classified into two groups. One was a gaseous form and the other was a dissociated form. Carbon dioxide was considered to be a weak acids when it dissociated into ionic form, and the dissociation of carbon dioxide was expressed in Henderson-Hasselbalch's equation. The results in this study showed that those rules concerning the dissolution and dissociation of carbon dioxide held for a model liquid system.

By using the modified Severinghaus CO2 electrode, the relationship between partial pressure of carbon dioxide in effluent gas and that in culturing system was investigated.