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2742050 
Technical Report 
Effect of citric acid on the solubility of caffeine in aqueous solution 
Anderson, JR; Pitman, IH 
1979 
IPA/81/445058 
J 
REF 8 
117-122 
English 
IPA COPYRIGHT: ASHP The solubility of caffeine (I) in aqueous solutions of citric acid (II) with pH values in the range of 0-10 was studied. Results suggest that unionized II forms one or more molecular complexes with I in which the stoichiometric ratio of II to I is 1.0. The complex that eventually precipitates out of such solutions is identical to the caffeine citrate of commerce. Mono-, di-, and tri-ionized II depressed the solubility of I by what appeared to be a specific salting out phenomenon.