Kuroda (2) reported an approximate solubility of the three isomeric monochlorophenols in water in the range of 2 percent. More support for the work of Sidgwick and Turner is given by the work of Blackman et al. (3) and that of Mulley and Metcalf (4). The data reported in these two works are in good agreement. For an assumed solution density of 1.0 g/cm³, a value of 27 g(1)/kg results from the work of Blackman et al. and a value of 26 g(l)/kg results from the work of Mulley and Metcalf.

     In reviewing the work of Blackman et al. it should be stressed that the solubility was determined at a pH of 5.1, a condition being controlled by the addition of a phosphate buffer (a KH₂PO₄ solution). However, the effect of the buffer solution can be minimized since the pH of a saturated 4-chlorophenol solution can be assumed to be of the same magnitude as that of the buffer and the ionic effects can be assumed to be quite low (as reported by Robinson and Stokes (5), the pK for 4-chlorophenol in water is 9.4). Even so, one should remember that the pH does exert some influence on the solubility of protolytic solutes such as 4-chlorophenol and attention should be paid to agents in the solution which change its acidity. The data are shown in Figure 1.

     The solubility of 4-chlorophenol in water at normal temperatures has a reliable value as deduced from the three references. However, the mutual solubility of 4-chlorophenol and water as reported by Sidgwick and Turner over its entire temperature range must be considered tentative because of the lack of other supporting data.

     The following solubility of 4-chlorophenol in water is tentative and based primarily on the reported value of Blackman et al.:

Experimental Data:   (Notes on the Nomenclature)