Aging Effect of Nascent Hydrogen on the Magnetic Moment of Hardened Steel Magnets.—When magnets, well seasoned by repeated heating and cooling, are exposed to the action of nascent hydrogen by being made cathodes in a sulfuric acid bath, the magnetic moment decreases, reaching in time a permanent value from 5 to 20 per cent. less than the original moment. The aging process is accelerated by raising the temperature of the electrolyte, the total time required being only one hour or less at 60° C. For drill rod (carbon 1.2 per cent.), quenched from 800° C., the change occurs gradually; but for tungsten magnet steel most of the decrease occurs suddenly after an exposure which, for the electrolyte at 60° C., varies from 3 to 15 minutes as the quenching temperature is increased from 700 to 850° C., the corresponding sudden changes in moment decreasing from 19 to 4 per cent. The behavior of spring steel (carbon 0.8 per cent.) is very similar, but the sudden changes occur later. After aging in this way, hammering the magnets has practically no effect.