DEVELOPER BEING LESS SUSCEPTIBLE TO OXIDATION AND METHOD FOR PREPARATION THEREOF

摘要

A developer being less susceptible to oxidation, characterized in that it contains a mixed salt of a divalent iron and a trivalent iron dissolved therein; and a method for preparing the developer. The mixed salt of a divalent iron and a trivalent iron preferably comprises a compound which is prepared by a method comprising dissolving magnetite in a conc. hydrochloric acid, followed by neutralization and concentration, to form a crystal, and then adding the crystal to a solution of magnetite in a conc. hydrochloric acid, and is preferably contained in the developer in a concentration of 0.25 X 10−8 mg/liter to 0.25 X 10−10 mg/liter.