LAWS OF SOLUTION 7 



motic pressure that is lower than that of serum in approximate proportion 

 to the readings on the tube in the two cases, and vice versa. 



The above apparatus, called a hematocrite (Fig. 2) has been very ex- 

 tensively used in the collection of data concerning the relative osmotic 

 pressures of different physiological fluids. 



Hemolysis 



Another way for determining the relative osmotic pressure of dif- 

 ferent solutions consists in placing equal amounts (a few drops) of 

 blood in a series of test tubes containing solutions of different strengths, 

 and after allowing the tubes to stand for some time, noting in which of 

 them laking of the blood corpuscles occurs. In solutions which are 

 isotonic or hypertonic with the contents of the corpuscles, the latter 

 will settle to the bottom of the tube and the supernatant fluid will be 

 untinted with hemoglobin, but in solutions which are distinctly hypotonic, 

 the sediment will be less distinct and the supernatant fluid red. 





Fig. 2. Hematocrite. The graduated glass tubes are filled with the two specimens of 

 blood, or corpuscular suspension, and then rotated rapidly by a centrifuge. The relative heights 

 at which the corpuscular sediment stands in the two tubes is proportional to the osmotic 

 pressures of the fluid in which the corpuscles are suspended. 



By noting (1) the lowest concentration (percentage composition) of 

 the solutions in which the corpuscles sink to the bottom and leave the 

 supernatant fluid colorless, and (2) the highest concentration in which 

 the corpuscles when they settle leave the supernatant fluid tinted red, we 

 can determine the limiting concentrations for solutions of different .sub- 

 stances. Thus, with bullock's blood the following results were obtained 

 (Hamburger) : 



SUBSTANCE 



PERCENTAGE STRENGTH OF SOLUTION IN WHICH 

 I II 



SUPERNATANT FLUID SUPERNATANT FLUID 

 WAS COLORLESS WAS RED 



