717 



was promoted by adding a large quantily of finely powdered anhydride. 



If we compare these results with those of Tabic 2, we notice 

 that now indeed the anhydride-concentration has risen : as the acid 

 concentration also lies higher this is evidently also promoted by the 

 concentration increase of the other pseudo-component. 



It now still remained to be seen whether the internal composition 

 of the liquids which are shaken with anhydride oidy, agrees with 

 the conclusions drawn from the above experiments. 



In Table IV is shown the result of a measurement. 



From this we notice that the large total-solubility found when 

 shaking with anhydride is mainly an acid-solubility. In another 

 series, for instance, 43.6 acid : 7.7 anhydride was found for the 

 composition at the greatest total solubility. More than the sixth part 

 can therefore never be put to the account of the anhydride. As 

 originally no solid phthalic acid is present as a solid phase we are 

 presumably dealing here with supersaturated solutions, although on 

 the other hand, anhydride and acid seem to promote each others 

 solubility. It is therefore, intelligible that, after the maximum has 

 been attained we can plainly observe the separation of the phthalic 

 acid in the liquid and also that the liquidum phase gets impoverished 

 both in acid and anhydride. As regards the acid this is presumably 

 the case in a much higher degree than indicated in Table 4 as the 

 withdrawal, after the maximum concentration has been passed, 

 always takes a few minutes on account of the clogging of the filter 

 by the deposited exceedingly- finely divided phthalic acid. In the 

 meanwhile of course, a little of the anhydride from the clear 

 liquid in the conductivity vessel becomes hydrated again before the 

 measurement could be executed and thus a somewhat too high acid 

 and a somewhat too low anhydride concentration is found. 



