64 



ILLINOIS BIOLOGICAL MONOGRAPHS 



[184 



seem to be the concentrations used by most pharmaceutical workers who 

 have tested the goldfish method of Pittenger and Vanderkleed.) The time 

 reqmred to kill the goldfish will generally tell one whether the solutions are 

 too strong or too weak. See discussion of survival time curve, page 48. If 

 the curve approaches a straight line and is at an angle to the X-axis the solu- 

 tions are of the most effective concentration. A second method consists in 

 running only one experiment, determining the survival time of the goldfish, 

 and applying this datum to the survival time curve (Curve LIJM, Fig. 1) 

 or to the curve of the constant (Figs. 25 and 26) and reading directly the 

 approximate concentration of the unknown. These curves also show the range 

 of concentrations (concentrations represented by the portions of the curves 

 A to B) most advantageous to use. 



TABLE XXXIII 



0.246 N. Potassium Chloride 



*Fish was not dead when taken out of the solution 



**Fish was inactive and on side for about 1/2 minute or less immediately after being 

 placed in solution 



