On the Irreversibility of Gas Absorption found in various kinds of Irons. Gas absorption experiment has been carried out with various kinds of iron and its alloys to investigate the effect of impurity and heat treatment. The result of experiment show that virgin iron, when it contains no other metallic element, behaves toward gas reversibly, while impure iron behaves toward gas irreversibly. That is, pure iron absorbs the same quantity of gas whether it is once heated in the gas or not while impure iron absorbs the gas in less amount when it is once heated in the gas in comparison with the virgin iron.

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In charpy machine, the low-temperature impact test was carried out on a series of carbon steels in their various heat treated conditions, and the cause of low-temperature brittleness was systematically investigated.
It was found in the test that the sub-zero temperature brittleness is caused by iron carbide in steels, and the critical temperature (the temperature at which the brittleness sets in) varies in a wide range in accordance with the form as well as the quantity of the carbide. An extremely low carbon steel, in the quenched and tempered states, shows the critical temperature below -120°C. The low-temperature brittleness of this steel is an inherent characteristic of ferrite itself, and not due to the carbide which is so small in quantity and exists in an uninfluential form.
Steels containing a comparatively higher amount of oxygen show a greater susceptibility to subzero temperature brittleness. The effect of oxygen is particularly remarkable in low carbon steels.

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A rapid method for measuring the residual stress in steel ingot is described. Results of measurement made on several steel ingots in their various cooling conditions show that the residual stress increases with the cooling velocity. At the same cooling condition the stress in carbon steel ingot is considerably higher than that in nickelchromium steel ingot, showing that the transformation stress counteracts the thermal stress in nickel-chromium steel but not in carbon steel.
An attempt is made to give mathematical explanation of experimental results.

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Cd-Zn-Mg Alloys, containing a large ammount of Manganese, are considerably resistable, as AZG or AZF, to 3% of salt solution. If these alloys are, however, beated at about 200°C in air after machining, their surfaces are covered with a certain film which is much more resistable as described below.
The average weight loss of the sample which is composed by Cd 4%, Zn 3%, Mn 1·8% and Mg rest %, and heated at about 200°C, is 0·9% to its initial weight of 35 grs (test piece for tension test) by immersion in 3% of salt solution for 28 days and its strength decreased from 23kg/mmmm². to 19kg/mmmm². And the corrision which has taken place at two or three pits would be caused by defects of the film, i.e. pitting corrosion.
On the contrary, the unheated one, that brings 1·3% of weight loss and 7kg/mmmm² of reduction of strength, has been corroded generally around the surface.
For the study of effects of Cd and Zn on this resistable film, many compositions of Cd-Mn-Mg and Zn-Mn-Mg alloys were prepared. Each of them, heated at 150, 200, 250°, and 300°C was compared as to its resistibility qualitatively with the unheated one by means of immersion in 3% of salt solution.
The results obtained are that Zn up to 2% is harmless on this film, while Cd up to 6% aids to form this film, and the more manganese it contains, the more effective is the film. About 200°C is the best temperature for heating to produce this film.

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The corrodibility of mangan-magnesium alloys can be approximately vanished by solution treatment and quenching. The addition of lithium improves this property. The addition of the other elements is injurious. The injuries are less in the case of zinc, cadmium or bismuth. The corrodibility of these alloys and AZM, quenched and annealed are studied.

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