Prideaux. — On Kauri-resin. 



371 



Free Acids. 

 I employed the usual method with extra precautions, ren- 

 dered necessary by the insolubility of the resin. Took a very 

 small portion of the resin and let it steep in absolute alcohol 

 for about half an hour. Then boiled under a reflux condenser 

 for about a quarter of an hour, and let it cool and remain over 

 night before titrating. The resin formed a kind of emulsion 

 with alcohol, but was not completely dissolved even by a very 

 large excess. The neutralisation values kept increasing on 

 dilution, but the rate of increase got slower. I took for final 

 the values obtained at a dilution just not too great to allow 

 the pink colour of the phenolphthalein to be perceived. The 

 figures represent the number of cubic centimetres of normal 

 NaOH required to neutralise 100 grams of the resin. 



