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XCVI. The Solubility of Calcium Carbonate in Water. By 

 James Kendall, M.A., B.Sc, Vans Dunlop Scholar in 

 Chemistry, University of Edinburgh* . 



nPH.E determination o£ the solubility of calcium carbonate 

 JL in water is evidently, apart from its purely chemical 

 interest, a very important problem, owing to the application 

 of tiie values obtained to the results of water analysis, and 

 to their bearing upon the study of geological formations. 

 Although much work has been done upon the subject, no 

 satisfactory measurements have been made. The main dif- 

 ficulty in the determination of exact results lies in the fact 

 that, in consequence of the extremely small degree of solu- 

 bility, it has been necessary to adopt indirect methods for 

 its estimation. Thus Kohlrausch and Eose {Zeit. phys. Chem. 

 xii. p. 234 (1893)) included calcium carbonate in their 

 investigations on the solubility of difficultly-soluble substances 

 in water by means of the electrical conductivities of the 

 saturated solutions. Calcite, arragonite, and the amorphous 

 form of the carbonate were examined at temperatures ranging 

 from 2° C. to 34° C, and provisional figures for the solu- 

 bilities and temperature coefficients were given. The method 

 and its application were further elaborated in a second paper 

 published ten years later {Zeit. phys. Chem. xliv. p. 197 

 (1903)); but in the final paper (Zeit. phys. Chem. lxiv. p. 129 

 (1908)), giving the calculation of the actual solubilities of 

 the substances examined from the observed conductivities, 

 the figures for all carbonates were omitted. This was because 

 the errors introduced by the correction necessary for the 

 conductivity of the water itself may be greatly augmented 

 owing to our lack of knowledge of the influence of the 

 C0 3 " ion. Any values obtained could therefore only be 

 regarded as rough approximations. The provisional figures 

 of the first paper were consequently retained. 



Holleman also, simultaneously with Kohlrausch and Rose 

 {Zeit. phys. Chem. xii. p. 125 (1893)), applied conductivity 

 measurements to the determination of the solubility of calcium 

 carbonate, and obtained similar results. 



Foote {Zeit. phys. Chem. xxxiii. p. 740 (1900)), using 

 other indirect methods to determine the ratio of the solu- 

 bilities of the two crystalline forms, confirmed the provisional 

 figures of Kohlrausch in this respect, but made no actual 

 solubility measurements. 



In water analysis, the determination of the amount of 

 calcium bicarbonate present in a given sample (?'. £., the 

 * Communicated by Prof. J. Walker, F.R.S 



