AND CALCIUM CARBONATE, ETC., OF WATER SOLUTIONS. 253 



By considering the bicarbonate to ionize like the acetate, we easily find 

 by trial that ^CaCHCOg)^ has a concentration of 0.0196 equivalent, whose 

 degree of ionization is found from the conductivity curve for calcium ace- 

 tate to be 78.5 per cent 



0.0196X0.785 = 0.01538 calcium ion equivalent, 



as required by the isohydric principle.^ 



Thus we find the degree of ionization of the calcium bicarbonate to be 

 78.5 per cent. The ionized portion of the bicarbonate is 0.00015 gram 

 molecule per liter, as was found above; consequently the total amount of 

 calcium bicarbonate in 1 liter is 0.00015/0.785 or 0.00019 gram molecule. 



A solution saturated with gypsum and calcium bicarbonate and carbon- 

 ate at about 18° under a partial pressure of 0.0003 atmosphere would contain 

 therefore 1.9 X 10~* gram molecule of calcium bicarbonate. Such a solution 

 by evaporation would deposit an equivalent amount of calcium carbonate, 

 or 0.019 gram of calcium carbonate per liter,^ and gypsum deposited by 

 evaporation from such a solution would be contaminated with 0.019/2.07 

 or 0.9 per cent of calcium carbonate (referred to the anhydrous gypsum).' 



For a solution saturated at 18° with gypsum and with calcium carbon- 

 ate and bicarbonate under a partial pressure of carbon dioxide 10 times as 

 great as the present average value in the atmosphere, the proportion of 

 calcium bicarbonate in solution can be calculated in a similar fashion. As 

 a first approximation we have 



= -y/ 10X0.0003 = 0.00095 



Since Cca is iCHcOa* the concentration of calcium ions in solution would 

 be close to 0.00769 + 0.00047 or 0.00816, and consequently in the saturated 

 solution the maximum value for the carbonate ions is 



1.26XlO-« _ , 



^^0^— 0.00816 1-^^Xl" 



Introducing this corrected value into the above equation, we find 



Chco3 = 0.00916 and Cca = 0.00046 



The degree of ionization for the calcium bicarbonate is found by the 

 method used above to be 78 per cent and the total calcium bicarbonate, 

 ionized and non-ionized, in 1 hter, is 0.000458/0.78 or 0.00059 gram molecule. 



A solution saturated with gypsum and calcium carbonate and bicar- 

 bonate at 18° under a partial pressure of 0.003 atmosphere would contain 

 therefore 5.9 X 10"* gram molecules of calcium bicarbonate per liter, and by 



» 20 c c of a 0.0196 equivalent or 0.0098 molar solution of calcium bicarbonate would 

 contain 0.000196 gram molecule and 0.000196X0.785 = 0.00015 Cca, the total concentra- 

 tion of calcium ions derived from the bicarbonate in solution. The bicarbonate lomzes as if 

 it were all dissolved in about 20 c.c. water. , 



» The amount of calcium carbonate in solution in 1 hter is so minute as to be negligible. 



' Cf. Findlay, loc. dl. 



