Fire, chemistry dusts

Technetium and rhenium differ markedly from manganese, but they are very similar to each other. They have little cationic chemistry, few compounds in the oxidation state II, more extensive chemistry in the IV and V states. The metals resemble Pt in their appearance (usually, however, they are in the form of a grey powder) they tarnish slowly in moist air, do not react with water. Metal dust is a fire and explosion hazard. 

Chemistry does not limit itself to spaces called reactors. Considerable quantities of dust, mist, and vapours may be transferred to vent lines and fumehood ducts, possibly accumulating and reacting there for years. In consequence fires and explosions can start, or blockages form. Vent lines would be better for occasional scrubbing down. See Perchloric acid Fume cupboards See Silver nitrate Sodium dithionite... 

Potassium sulfide, K2S, is a binary salt. It is a red or yeUow-red crystalline mass or fused solid. It is deliquescent in air, which means it absorbs water from the air, and it is also soluble in water. Potassium sulfide is a dangerous fire risk and may ignite spontaneously. It is explosive in the form of dust and powder. It decomposes at 1562°F and melts at 1674°F. The specific gravity is 1.74, which is heavier than air. The four-digit UN identification number is 1382. The NFPA 704 designation is health 3, flammability 1, and reactivity 0. Potassium sulfide is used primarily in analytical chemistry and medicine. 

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