In the study on the effects of various salts and pH on Donaggio reaction the author obtained the following results. 1. In the case loaded with 1% table salt solution the Donaggio value is reduced to one half and in the case with 7% salt solution it is decreased to 1/4. 2. As for the effect of ions, Na(+), K(+), and Mg(+) show an in hibitory action on the Donaggio reaction. 3. As for anions Cl(-), SO(-)(4) and PO(-)(4) likewise show an inhibitory action on the reaction. 4. At pH between 7.4 and 9.0 the Donaggio reaction is strongly postivie while at pH between 5.8 and 3.0 or between 10.0 and 11.0 the reaction is weakly positive. However, at pH under 2.0 and over 12.0 it is negative.