Measurements of the film-clearing time in practical monobaths with near infrared ray to which most of conventional photographic materials are not sensitive were performed, and the dependence of film-clearing time on pH was investigated. After trials of several experiments, the automatic film-clearing recorder has been assembled with a near infrared source, a water-jacket cell, a Ag-0-C_s photo tube, an amplifier and a recorder. The filmclearing time in a P-Q monobath is changed remarkably by alterations in pH, and it occurs by the presence of developing agents. Developing agents slow down the rate of fixing in monobaths below pH 11, and don't change above pH 11.