652 Scientific Proceedings, Royal Dublin Society. 



For observing the electrical conductivities a Kohlrausch apparatus (by 

 Kohler of Leipzig) was used. Both viscosity and conductivity determinations 

 were made at 0° C. 



Dixon's (5) thermo-electric method was employed to ascertain the freezing- 

 points of the sap. 



The Application of the Viscosity Correction to the Conductivity of the Leaf-Sap 



of Aucuoa japonica. 



In Table I the results are recorded of an experiment which was carried 

 out on the leaf-sap of Aucuoa japonica. The leaves from which the saps were 

 extracted were gathered from shrubs growing in the Botanical Gardens and. 

 grounds of Trinity College, Dublin, the former located in the inner suburbs 

 and the latter in the city. Experiments 1-6 were made on leaves from the 

 College grounds, and 7-9 from the Botanical Gardens. In order to render the 

 protoplasm permeable, the leaves were frozen at approximately - 16° C; the, 

 sap was then extracted by pressing the leaves between silver discs. 



About 350 c.c. were extracted for each experiment; after filtration,, which 

 occupied several hours, 1/8625 gm. of potassium chloride was dissolved in 



' 'N\ 



250 c.c. of thesap; an aqueous solution of this concentration I — jhas a eon^ 



ductivity at 0° of - 00715. In Table I the following nomenclature has been' 

 employed: — 



V = the relative viscosity of the sap. ■• •.'•'•. 



C s - the conductivity of the sap. 



C s + KC i = the conductivity of the sap in which the potassium chloride was 



dissolved. 

 C ECl = the conductivity shown by the potassium chloride dissolved in the 



sap, and is numerically equal to C s + ECl - C s . 

 C KC i = C EC i after the application of the linear correction for the viscosity of 



the sap, and should, if the correction is justified, approximate to 



the conductivity of an aqueous decinormal solution of potassium 



chloride, viz., to 0'00715. 

 C" s = the conductivity of the sap to which a similar correction for viscosity 



has been applied. . . 



A c = the depression of the freezing-point, which would be produced by a 



potassium chloride solution, having a conductivity equal to that 



of C v s , thus affording an approximate index of the contribution of 



the electrolytes to the total depression, and so of course to the 



osmotic pressure. 

 A = the depression of the freezing-point of the sap. 

 A- A e = the depression due to the non-electrolytes of the sap, e.g. sugars. 



