in Aqueous Salt- Solutions. 



381 



when we substitute for the concentration of the base that of 

 the sodium phosphate. 



Instead of K we may write kfi, where y, is a factor which 

 expresses the ratio of the amount of free alkali present to 

 what would be present if the hydrolysis of one sodium atom 

 was complete. 



Equation (8), on integration, gives the solution 



c^c 2 lo g nat S=3- c=c; lognat - feS = k ^- f o), 



or 



log 



C 2 — #?o 



log 







'#0 



0-4343 ^(*i-'*o)(0-CI 2 ), . (9) 



C 2 —x l C — x x 



from which we can calculate /jl at the time t\. 



In order to determine fi at the commencement, the different 

 values of \x> are plotted against the times, and the curve so 

 obtained prolonged. The point at which it cuts the axis for 

 the time £ = gives the value of fju at the commencement. 



Experiments have been made which show that Na 2 HP0 4 is 

 only slightly hydrolysed ; so if we neglect this and assume 

 that the equation 



Na 3 P0 4 + HOH = Na 2 HP0 4 + NaOH 

 represents the possible quantity of caustic soda which can be 

 formed in the solution, then 100 juu represents the percentage 

 amount of the caustic soda which actually exists in the solution. 



The following experiments were made with a jfo molecular 

 normal solution of trisodium phosphate at 24 0, 2 0., at which 

 temperature the coefficient of velocity of reaction for caustic 

 soda is 6*28. The concentrations are expressed in ^h^ of a 

 gram-molecule per litre, and the employment of phenol 

 phthale'in enabled the titrations to be made pretty accurately. 





50 



(mol.) 



Trisodium Phosphate. 





t. 



I. 



II. 



C 2 -x. 



X, 



O-x. 



/*. 







3-81 



3-81 



3-81 



o-oo 



4-87 





2 



2-93 



2-95 



2-94 



0-87 



4-00 



0945 



4 



241 



245 



2-43 



1-38 



3-49 



0-882 



6 



2-06 



2-03 



2-04 



1-77 



3-10 



0-873 



8 



1-82 



1-77 



1-79 



2-02 



2-85 



0-831 



10 



1-58 



1-55 



1-56 



2-25 



262 



0-827 



12 



1-35 



1-40 



1-37 



244 



243 



0-827 



16 



1-12 



1-14 



1-13 



2-68 



2-19 



0-788 



20 



091 



094 



0-93 



2-88 



1-99 



0780 



24 



0-79 



0-80 



079 



3-02 



185 



0764 



30 



063 



0-66 



0-64 



3-17 



1-70 



0-73S 



Phil. Mag. S. 5. Vol. 35. No. 215. April 1893. 2 D 



