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All iron nitrides are gray powders.
Iron has five nitrides, Fe2N, Fe3N1+x, Fe4N, Fe7N3 and Fe16N2. They are crystalline, metallic solids. Group 7 and group 8 transition metals form nitrides that decompose at relatively low temperatures - iron nitride, Fe2N decomposes under loss of molecular nitrogen at about above 400 °C and formation of lower-nitrogen content iron nitrides. They are insoluble in water.
When heated to decomposition, or exposed to humidity, iron nitride may emit toxic fumes of ammonia. It is considered a moderate explosion hazard. Inhalation of iron nitride dust or powder may cause irritation to the respiratory system and possibly acute iron poisoning or iron pneumoconiosis.
Iron nitrides also make the strongest naturally magnetic material.