When expired chemicals are found, the first consideration is to **safely dispose of**, rather than directly using their reactivity. The following step-by-step guidance on how to deal with and potential scientific use： --- ###️️** Step 1: Safety assessment** 1. **Identify chemicals** - Check the label or MSDS (material safety data sheet) to confirm the chemical name, composition and expiration time. -**Common risks of expired chemicals**： -Hydrogen peroxide (decomposed into water and oxygen, the container may be pressurized) -Organic solvents (such as ethanol and acetone, which may form explosive peroxides) -Strong acid/alkali (risk of leakage from corrosive containers). 2. **Danger signal** -The container expands, changes color, crystallizes or smells→ ** Isolate immediately ** and contact a professional organization (such as a fire department or an environmental protection company). --- ###️**Step 2: Legal disposal** Expired chemicals are **hazardous waste**, and it is strictly prohibited to dispose of or pour into the sewer at will. -**China**: Contact the hazardous waste treatment unit designated by the Local Bureau of Ecology and Environment. -**Other regions**: Look for “Hazardous Waste Disposal Services” or community chemical recycling activities. --- ### 🧪**Possible scientific use (only for professionals)** If it is confirmed that the chemical is stable in nature and harmless, **Under the guidance of professionals** You can try： 1. **Educational demonstration** -Expired copper sulfate (blue crystal)→ Crystallization experiment or electrolytic copper plating. -Expired potassium nitrate (KNO→) → sugar rocket fuel (professional knowledge required). 2. **Harmless transformation** -Use acetic acid (vinegar) and baking soda→ simulate volcanic eruptions (CO生成 generation). -Expired iron salt + potassium ferrocyanide→ Prussian blue precipitation (art pigment). 3. **Recycled metal** -Silver-containing compounds (such as silver nitrate) → Chemical reduction to extract the elemental silver. --- ### ***Important reminder** -**Experiments are prohibited in the home environment**: Most chemical reactions release toxic gases or cause fires (such as organic solvents + oxidants). -**Legal risks**: The unauthorized synthesis of specific substances may be illegal (such as explosives and drug precursors). It is recommended to hand over chemicals to professional institutions, safety first! If you wish to explore chemical experiments, you can purchase fresh reagents from legal channels and wear protective equipment. (For specific chemical safety recommendations, please provide a detailed name. ）