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XLVL 



ON SOME FACTORS AFFECTING THE CONCENTRATION OF 

 ELECTROLYTES IN THE LEAF-SAP OF SYBINGA VULGARIS. 



By T. G. MASON, Sc.B., MA. 



Read Novembeu 25. Published December 12, 1919. 



Considerable fluctuations in the concentrations of electrolytes, as shown by 

 conductivity observations, have been recorded by Dixon and Atkins (4) in 

 the leaf -sap of Syriiiga vulgaris from different localities. It was hoped that a 

 more extended examination might throw some light on the factors responsible 

 for these fluctuations, and possibly contribute something to an appreciation 

 of their physiological significance. A distinction between the electrolyte 

 content and ash content must be drawn, since the former is mainly due to 

 inorganic salts in solution in the cell-sap, whereas the latter embraces not 

 only the mineral elements in solution in the sap, but also those constituents ' 

 which have been removed from solution in the course of metabolism. 



Some doubt was felt as to the value of observations of the conductivity of 

 the sap as a means of determining the amount of electrolytes present, unless 

 the effect of viscosity was taken into consideration. Consequently some 

 preliminary experiments on this subject were undertaken. 



It has been established that for most organic solvents the mobility of the 

 ion varies inversely with the viscosity ; and though this is only approxi- 

 mately true for salts in aqueous solution, it is clear tbat allowance for this factor 

 would add considerably to the precision with which the amount of electrolytes 

 in the sap could be determined. In order to gauge the value of this relation- 

 ship for the sap, the following experiments were made: — 



Method. 

 The method adopted was to observe the conductivity of a certain con- 

 centration f — - J of potassium chloride dissolved in the sap, and by comparing 



this with the conductivity of the same concentration in aqueous solution the 

 loss due to the viscosity of the sap could be determined. 1 ' A viscosimeter of the 

 Ostwald type was employed in making determinations of the viscosity of the 

 sap ; the results of these determinations are expressed as relative viscosities. 



..... / jsf\ .• 



1 This is not strictly true, since I — ) potassium chloride is not as completely disso- 

 ciated in the sap ; the magnitude of this error will depend on the concentration of 

 potassium and chlorine ions present in the sap. 



SCIENT. PEOC. R.D.S., VOL. XV., NO. XL VI. 5 K 



