The electric resistances of oxidizer and reducing agent powders, especialy metal powders used for pyrotechnic raw materials were measured with the direct current method. One metal powder with the electric resistance below 100 Ω showed the electric resistance above 109Ω, though most of metals had low electric resistance below lOO Ω. It was also observed that some metal powders had only high resistance above 109Ω. Such large change of the electric resistance may be attributed to the thickness of oxide films formed on metal powder surfaces. It was suggested that if the films were thin, the electric resistance of metal powders were determined by the contact resistance among metal particles, and if they were thick, the electric resistance of metal powders were detemined by the electric resistance of their oxide film. Most of oxidizers had electric resistance ranged from 106 to 109Ω. But some oxidizers showed the electric resistance above 109Ω and others did below 106Ω. It was deduced that the electric resistance for oxidizers were determined by their own resistance.
火工品組成物原料の還元剤, 特に金属粉, および酸化剤などの粉体の電気抵抗を直流法によって測定した｡ 金属粉は約100Ω 以下の電気抵抗を示すものが多いが, マグネシウムのように同じ金属粉がその粒子の表面状態によっては109Ωを超える場合もあった｡ また, アルミニウムのように109Ωを超える電気抵抗だけしか示さない金属粉もあった｡ 酸化剤粉体は106 - 109Ωの中間の電気抵抗を示すものが多く, それよりも高いまたは低い電気抵抗を示すものもあった｡ 金属粉では, 個々の粒子の酸化被膜の状態が粉体の電気抵抗に関係する。 すなわち酸化被膜が薄い場合には粒子間の接触抵抗が,厚い場合には酸化被膜自体の電気抵抗が粉体の電気抵抗を決定すると考えられた｡ 酸化剤では粒子の固有抵抗が粉体の電気抵抗の支配因子となる｡