The alkyl esters of 4-hydroxybenzoic acid (parabens) are widely used as preservatives and antimicrobial agents.  Significant variability in K_a for phenol hydrogen dissociation of different alkyl 4-hydroxybenzoates has been reported in the literature.  The literature also indicates no variation in Hammett's sigma values for all esters, regardless of size. Since sigma is calculated from the dissociation constants for substituted benzoic acids (K_X) and of benzoic acid (K_H ): sigma = log(K_X / K_H), it is reasonable to expect that all the parabens would have the same (or nearly the same) Ka.  One possible explanation for the discrepancy is a solvent effect, the s data was obtained in water, but the parabens data were obtained in 95% ethanol.  Previously, we presented information demonstrating that the Ka values for three of the parabens were different in largely aqueous media.  Limits from instrumentation and solubility have been addressed and we are reporting Ka values for additional parabens.