The determination of serum acid and alkaline phosphatase activity with 4-aminoantipyrine (A.A.P.).

C6H5 Gottlieb and Marsh (1946), using alka:ine ferricyanide as the oxidant, devised a method for the estimation of certain phenolic fungicides with A.A.P. The procedure was modified by Grifols (1951) for the determination of phenol in the measurement of alkaline phosphatase activity in body fluids. This author made a careful study of the factors which control the development of the colour and his results showed good correlation with those obtained by the method of King (1951). Advantages claimed for the method were that the reagent did not react with proteins, thus obviating their precipitation during the estimation, and also the colour development was comparatively rapid. The use of A.A.P. as a reagent for phenol appeared to be of potential value especially if its use could be extended to the estimation of serum acid phosphatase activity. Considerable modification of the original Grifols procedure was found to be necessary in order to measure both alkaline and acid phosphatase activity in blood. The use of calibration curves, the stability of the colour, and the effect of the presence of serum