PURPOSE:To obtain analytical value having a high accuracy by compensating a drift of zero point providing a two-light pass length photometer which compares photometries by being allowed to change a light pass length of a flow cell periodically with two steps in said colorimeter with a two- wave length photometric means. CONSTITUTION:The colorimeter is adapted to constitute to compensate a change of zero point during its continuous measurement by being changed a distance between opposite faces of window plate glasses 12a and 12b of a flow cell, a light pass length. In other words, an absorbancy based upon the case when the light pass length is longer, changes in proportion to the difference between the light pass length. When the change of the light pass length is repeated in short time, the contamination degree between the glass plates, 12a and 12b, during this time is regarded to be invariable to the influence of the contamination of the window glass plate 12 in flow cell 4 is compensated. Further, if there is no rapid change of the concentration in a measured liquid within a short period wherein the light pass length is changed, the measuring is adapted to be performed always compensating the change of the zero point since the photometries are conducted by a comparison method with longer light pass length as a reference data. An analytical value having a high accuracy can be obtained by compensating a drift of zero point through such constitution.
展开▼
