364 Mr. S. B. Schryver and Miss M. Hewlett. Investigations 



The results of the erosive action of different salts on the gel containing 

 added potassium chloride are shown graphically in fig. 1, where the concen- 

 trations of the eroding solutions are plotted as abscissas and the amounts of 

 erosion as ordinates. The curves obtained with gels containing other added 

 salts do not differ materially from this one. 



Concentration of Na CI '. solution 

 Fig. 1. 



It will be noticed that the curves possess a diphasic character, with two 

 minima and two maxima. The amount of erosion increases with increase in 

 the concentration of salt in the eroding solution up to a certain point 

 (3N/20 — 41ST/20). On increasing the concentration beyond this, the amount 

 of erosion diminishes, until it reaches a minimum (61ST/20 in the case of the 

 chlorides of potassium, magnesium and sodium, and 9N/20 in the case of 

 lithium chloride), when it is little more than that which takes place in the 

 presence of pure water. On increasing the concentration above this point the 

 erosion again increases. Eesults of this character have been obtained 

 constantly ; only a portion of them are recorded in this paper. 



There is a considerable variation in the effects produced by the various 

 salts in the eroding solution. The maximal eroding effect produced by the 

 lower concentrations, shown both by the amount of erosion and the breadth 

 of the " zone of instability " (as it is convenient to designate the interval 

 between the two minima of the curve), is produced by the lithium salt, 

 followed, in decreasing order of action, by the chlorides of sodium, magnesium 

 and potassium. It has been found by Stiles and Jorgensen* that the effect 

 * * Annals of Botany,' vol. 29, p. 349 (1915). 



