| Show color colors produced in iron investigation as to the cause of the production n of colors in tempering iron satisfactorily facto rily shows it to be due to the formation of thin films of oxide on the surface of the metal when it is heated in the presence of air it also appears that the oxide so produced Is I 1 practically transparent first because tile sequence of colors is what would le be expected in films of a transparent substance when the thickness of the films gradually increases also because of observations ions antho on the reflected light the color of which varies somewhat at different an chiefly because it is found folind that on increasing the temperature a little above the point necessary to produce dark blue the color gradually disappears and the surface though covered with more oxide becomes almost colorless again the colors being the result of oxidation it is probable ta that I 1 at the nature of the surface to be heated its freedom from any soiling and the length of time during which it is heated must exert a considerable influence on the shade produced new york telegram |
