﻿976 The Solubility of Calcium Carbonate in Water. 



As before, the values for the two highest dilutions show 

 that hydrolysis is there appreciable. The value of the con- 

 ductivity at infinite dilution may be taken as 108*0 ; taking 

 the velocity of JCa* 61*5, we have the velocity of the HC0 3 ' 

 ion equal to 46*5. 



Finally, the conductivity of solutions of calcium sulphate, 

 the values of which are also of importance in water analysis, 

 was determined. (Compare Kohlrausch and Holborn, Leit- 

 vermogen der Elektrolyte, p. 161 (1898).) Calcium sulphate 

 was precipitated by mixing dilute solutions of potassium 

 sulphate and calcium chloride, filtered off from the solution, 

 and thoroughly washed, A saturated solution at 25° C. was 

 prepared by rotating a small quantity in a well-stoppered 

 flask, half filled with water, in a thermostat for some days. 

 The liquid was obtained free from excess of solid by means 

 of a pipette fitted with a filter-cover ; its concentration was 

 determined gravimetrically by evaporating 100 c.c. carefully 

 to dryness in a platinum basin. The water used for dilution 

 had a specific conductivity of 1*2.0 X 10 ~ 6 , the whole of which 

 is subtracted for correction, and the corrected results are as 



below. 



The figures are the mean of two determinations. 



Conductivity. JCaS0 4 . 

 (Saturated solution at 25° C. u=32:50 ) 



V. 



Conductivity. 



325 



72-9 



65 



83-7 



130 



94-7 



260 



105 5 



520 



115-0 



1040 



1233 



2080 



129-2 



4160 



134-1 



8320 



1384 



I desire, in conclusion, to express my thanks to Professor 



Walker, at whose suggestion the above investigations were 



i • i 

 carried out, for his advice and assistance during the progress 



of the research. 



Chemistry Department, 

 University of Edinburgh. 



