248 



EQUILIBRIUM BETWEEN CARBON DIOXIDE OF ATMOSPHERE 



In table 4 the data are tabulated and the calculated values for-JKcacOs 

 given. Column 1 gives P the pressure of carbon dioxide in atmospheres, 

 column 2 the solubility of calcium carbonate as determined by Schloesing 



and expressed in gram equivalents of calcium bicarbonate i ^ — ^ jper 



liter. Column 3 gives the degree of ionization a of the corresponding 

 calcium acetate solutions, column 4 the concentration of acid carbonate 

 ions, Chco3> as calculated from the numb ers give n in columns 2 and 3. 



In the last column we have the values for -J KcaCOs ^^ calculated according 



to equation (31). 



Table 4. 



The mean value for \/ KcaCOs is 0.002325. 



The agreement among the values found for -^KcacOa under a partial 

 pressure of carbon dioxide ranging from 2Vcrxr atmosphere to 1 atmosphere 

 is excellent, and this agreement forms a very good test of the correctness of 

 the whole theoretical treatment, such a constant resulting from a consider- 

 ation of the conditions of equilibrium on the basis of the theory of ioniza- 

 tion.i ., 



From the value for vf KcaC03 = 0-002325, we find the solubility product 



'^'^^^ Cca X CcOa -= KcaCOa = 1 -26 X 10"^ (33) 



It may be pointed out that this method of determining the' solubility 

 product constant of calcium carbonate must be far more reliable thanadeter- 



* As Bodlaender {loc. cit.) points out, it is clear from the theoretical treatment that the 

 same equation applies to the effect of carbon dioxide on the solubility of other difficultly 

 soluble salts, such as barium carbonate, the only difference being that the solubility pro- 

 duct constant of barium carbonate (Cfia X CcOs = KRaCO;;) is substituted for the constant 

 for calcium carbonate. All the other expressions remain the same. Bodlaender has used 

 the results of Schloesing on the solubility of bari um carbo nate as affected by carbon diox- 

 ide to calculate in the same way the value for iX KBaCOs and obtained again an excellent 

 agreement among the values for the constant. Only the numerical value of the constant, 

 not the constancy of the results, is affected by the corrections made in this paper, namely, 

 in the value of the second ionization constant for carbonic acid and in the method of calcu- 

 lation of the degrees of ionization a. As the value for ]/ KfiaCOa is not of interest in this 

 investigation, the data were not recalculated. 



