Abstract
The amount of dissolved oxygen (DO) in water which is one of the important indices of water pollution is ordinarily determined by means of Winkler's method. Because of the manual analysis, however, the errors are liable to occur in the process of pre-treatment of sample or in the visual detection of a titration end point.
A new analyzing instrument which controls automatically the sample treatment and titration procedure was constructed to determine the amount of DO more accurately. The instrument consists of the following parts: devices to measure the volume of sample, to treat the sample, to titrate, to indicate the result and to control the system. By the use of a potentio-metric method with a constant current for detecting a titration end point, the construction of the detector is considerably simplified. A series of the measurement is performed according to a pre-determined program. A digital indicator gives the results of the analysis, that is, the concentration of DO and the volume of titrant used for titration.
The precision of the analysis is experimentally evaluated to be about ±0.02g/m3 in terms of the standard deviation over the concentration range of DO from 8.5 to 13.5g/m3 and no significant difference is observed between the results obtained by this method and by the manual Winkler's method.
