250 transactions liverpool biological society. 



Determinations of the Potential of Hydrogen-Ion 

 Concentration. 



This is the modern method of expressing the state of 

 acidity or alkalinity of a solution at any given moment as 

 distinct from the amount of added acid or alkali necessary to 

 move the reaction to a given position. It is a static thing 

 while the " Buffer Effect " or " Reactivity " is kinetic or 

 dynamic. It might be termed the reaction of the fluid as 

 distinct from its reactivity. The one expresses present position, 

 the other ease or difficulty of moving into another determined 

 position. 



It has been known for some time that sea- water is an 

 alkaline solution : this is stated by earlier observers such as 

 V. Bibra, 6 Gruignet and Telles 7 and Tornoe. 8 Later Natterer 9 

 observed that water from the eastern part of the Mediterranean 

 was coloured red by phenol-phthalein, and, unconsciously 

 foreshadowing qualitatively Sorensen's later colorimetric 

 method, was able to note by comparing the depths of shade of 

 pink that the deep sea- water was less alkaline than the surface 

 water. 



Ruppin 10 was unable to note any pink coloration in 

 water from the North Sea and Baltic, but as the water was 

 drawn in 1909 from points near Kiel, the water may well have 

 been contaminated sufficiently artificially to reduce slightly the 

 alkalinity and throw it below the value necessary to give any 

 colour reaction with phenol-phthalein. 



Loeb 11 found the water of the Atlantic Ocean at Wood^s 

 Hole to give a pink colour with phenol-phthalein, while the 

 water of the Pacific Ocean at Pacific Grove was less alkaline 

 and gave no pink colour with this indicator. 



Correlated with this, Loeb found the interesting fact that 

 unfertilised ova of Strongylocentrotus developed partheno- 

 genetically to a much greater extent in the more alkaline water 



