Lab funnels are designed for channeling substances from large containers into small containers. In general, funnels have a wide top that narrows into the base and a stem that extends downward from the base. Often made of borosilicate glass for heat resistance, some funnels are made of plastic, such as LDPE (low-density polyethylene), polyethylene, polystyrene, or polypropylene to provide resistance to particular chemicals or moisture. Some funnels may be sterile or autoclavable for reuse, and they come in a variety of capacities suited to their particular application, usually measured in milliliters.
Filling funnels prevent spilling powder or liquid when filling a small-mouth container. They are commonly made of glass or plastic and have angled sides. Filtering funnels, such as Büchner funnels or Hirsch funnels, have straight sides and incorporate a paper or glass disc that filters particles from a liquid through vacuum suction. They can be made of porcelain, glass, or plastic to withstand vacuum pressure and chemicals, and come in a variety of capacities, from 30mL to 350mL.
A separatory funnel (sometimes called a separation funnel, separating funnel, or sep funnel) is used for extracting different components of a solution or mixture into two solvent phases of different densities. Typically pear-shaped, they are usually made of glass for chemical resistance or borosilicate glass to withstand temperature changes, but they can be made of plastic such as polypropylene as well. Separatory funnels have a glass or PTFE stopper at the top. A stopcock valve is included at the base of a separatory funnel to help control the flow of material through the stem.
Addition funnels, also called dropping funnels, can be cylindrical and have a stopcock to slowly dispense liquids such as reagents one drop at a time. They may be graduated with milliliter markings that indicate volume. Some addition funnels have a ground glass joint at the stem to fit onto a flask or other container. Others have a side arm tube that extends from the top to the bottom of the funnel body to equalize the pressure inside the funnel and help liquids exit through the valve.