Solubility of Aspirin-Excess aspirin was equilibrated with aqueous buffer or buffered cetomacrogolsolutions by rotation in sealed cylinders in a watcrbath thermostatically controlled at 37 ZIC 0.1".After filtration through a jacketed filter-funnel,aliquots of filtrate were assayed for salicylic acidpresent due to hydrolysis. Further samples weremade alkaline with 0.5 N KOH, heated on a steambath for 60 min., reacidified with 0.5 N HC1, andassayed for total salicylic acid. The solubility ofaspirin was calculated from the difference betweenthe amount of salicylic acid present initially andthe amount found after complete hydrolysis.