A method for determining velocities of saponification

Abstract

A possible method of following the progress of a reaction in which electrolytes are involved is to measure the electrical conductivity of the solution at stated intervals. This method was employed by Walker and Kay in their investigation of the conversion of ammonium cyanate into urea, and is capable of a more extended application. The chief conditions for the convenient application of the method are: first, that there should be a considerable difference in conductivity between the initial and final systems, and second, that the change in conductivity should be proportional to the progress of the reaction. It occurred to me that these conditions would be well fulfilled in the saponification of an ester by a caustic alkali. The conductivity of the alkali, say sodium hydroxide, is much greater than that of the sodium salt produced by the saponification, owing to the high velocity of hydroxidion as compared with the salt anion. Since, too, sodium hydroxide and sodium salts of monobasic acids are approximately equally ionised under the same conditions, the ionisation in dilute solution remains practically the same throughout the saponification, and thus the alteration in the conductivity is almost exactly proportional to the progress of the reaction.