in Aqueous Salt- Solutions. 



377 





Concentration. 



A. 



Hydrolysis. 



— KCN 



0-00296 



0-00168 



0-00107 



0000557 



0-00804 



0-00596 



0-00465 



000338 



0-00294 



000131 



000074 



0-31 per cent. 



072 „ 



112 „ 



234 „ 



212 



3-17 



4-87 



7-10 



305 



6-69 



0-92 



N 



4 



N 



10 " 



N 



40 " 



^ (mol.)Na 2 C0 3 



N 



10 " 



N 



20 " 



40 " 



N 



-CLH-OK 



N 



50 " 



^(mol.)Na 2 B 4 7 ... 





A glance at the table will show that among the four sub- 

 stances examined the greatest amount of hydrolysis occurs in 

 the case of sodium carbonate. The numbers cannot pretend 

 to a very high degree of accuracy, chiefly on account of the 

 difficulties in obtaining suitable indicators for the titration of 

 the solutions, but the following regularity is easily discernible. 

 The amount of free alkali contained in the salt-solutions is 

 proportional to the square root of the concentration of the salt. 

 This is, however, not strictly true, but more nearly expresses 

 the truth the greater the dilution of the solution. A rough 

 calculation on the numbers for the two most concentrated 

 solutions of potassium cyanide shows that there is a deviation 

 from the law of about 13 per cent., whilst for the less concen- 

 trated solutions the deviation is reduced to about 4 per cent. 

 If the dilutions be plotted as ordinates against the percentage 

 amount of salt hydrolysed as abscissae, curves are obtained. 

 Fig. 1 represents the curves for potassium cyanide and sodium 

 carbonate. These curves enable us to see at a glance the per- 

 centage of salt hydrolysed at any given dilution. For example, 



