Final answer:
The best support for a separatory funnel is a metal stand because it provides stability, durability, and chemical resistance, making it suitable for supporting the funnel during liquid-liquid extractions in preparative chemistry.
Step-by-step explanation:
The best support for a separatory funnel, which is used in preparative chemistry for liquid-liquid extractions, should be stable, durable, and resistant to chemicals. Considering the properties required, the most appropriate material for a separatory funnel support would be metal (3). Metal stands are usually used in laboratories because they offer the strength to hold the funnel securely and are resistant to the various chemicals that might come into contact with them during the extraction process. Options such as glass or ceramic might not provide the necessary durability and could break more easily, while plastic might not have the required strength, especially if the funnel is full and heavy, and might also react with certain solvents. Hence, a metal support, often in the form of a ring stand and clamp, is typically used to securely hold a separatory funnel in place while allowing easy manipulation for shaking and phase separation as needed in chemical extractions.