716 



w 



Fia. 2- 



a lies at a greater concentration than b, the solution c contains more 

 acid than a. Looking at the presumably \evy slight solubility of the 

 anhydride and the fairly lai-ge reaction velocity of the hydratation 

 (four times greater^) than that of acetic and succinic anhydride) it 

 will be understood why in different experimental series were found 

 maximum values which mutually slightly differed. (Some tritration 

 values from different series: 41,4 — 41,4,44,0 — 44,3 — 44,5). Three 

 processes are taking place continuously : solution of anhydride, 

 hydratation thereof and crystallisation of phthalic acid. The latter 

 will no doubt take place spontaneously as a large quantity of finely 

 divided solid phase is present: the second takes place fairly rapidly 

 and the first is evidently not rapid enough to maintain the condition 

 of the point c. That appears from table 3 where this last reaction 



1) RivETT and Sidgwick i.e. 



