Incubation is accomplished for one hour at high temperature, or 3-5 hrs. 

 at low temperatures. The samples are then fixed with Lugol's solution or 

 formalin, filtered through membrane filters and 5-10 ml of physiological 

 solution is passed through the filter. After drying, the radioactivity of 

 microorganisms is determined and the data plotted. On the ordinate the 



- are plotted, where R is the radioactivity of the added organic 



values 



R 



substance, t - time of incubation, r - radioactivity of organisms in the 

 samples. The abscissa displays the concentration of the added organic sub- 

 stance. The points are connected with a line. The segment on the abscissa 

 to the left zero on the ordinate axis (Figure 5) corresponds to the reserves 

 of organic matter in the tested water. 



The rate of consumption of a given substance may be calculated by the 

 f omul a: 



w - r (A + S) 



2000 



35 70 105 140 



PHENOL CONCENTRATION, yug C/l 



Figure 5. Determination of the reserves of phenol in the water of 

 Kanskoe Reservoir by the method of Right and Hobbie. 



71 



the 



