抄録
Certain devices and experiments have been made in order to obtain an appropriate apparatus for measuring the resistance _??_r reaction of the aquatic organisms to the various polluting substances. A particular device has been made of the constant supply of the solution of a certain polluting substance and of acid or alkali solution for pH-adjustment. The apparatus is shown in Fig. 1 and 2, the one shown in Fig. ?? 2 being most feasible.
The efficacy of the apparatus has been tested by determining the deviation in concentration of a certain chemical during a fairly long duration. In the case of zinc sulfate in concentration of about 20mg per litre, the average deviations in the concentrations of four aquariums set up in parallel have been found, as is shown in Table 1, to be 2-3% in average, the maximum deviation being between+4.0_??_9.9%. The deviation in pH value has been of variance depending on the magnitude of the difference between pH value of tap water and the value to be maintained in the experiment, e. g., in an experiment at pH 4.5 the average deviation was 0.1, whereas at pH 5.7 it was 0.06. In the case of sodium sulfide, as is shown in Table 2, the average and maximum deviations in its concentration have been found to be 8.0%, and 19%, respectively. Taking into account individual differences of organisms, it will be apparent that by using the present apparatus the concentration of a polluting substance in running water can be maintained with such a constancy as to be sufficient in carrying out the biological test.
