Funnels are standard equipment in laboratories, but are also used for familiar tasks such as filling the kitchen salt shaker or pouring motor oil into your car engine. Laboratory funnels come in a variety of shapes and sizes and are used mainly to introduce liquids into laboratory flasks, beakers, test tubes and graduated cylinders. They are made to withstand the heat and chemicals commonly used both in school and commercial laboratories and are purchased from special suppliers. Laboratory funnels are measured in milliliters to indicate the amount of liquid volume they will accommodate.
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Standard plastic and metal funnels come in a variety of sizes useful for any task that requires pouring liquids or powders into containers with small openings. A common variation on the kitchen funnel is one with a wide, round opening that narrows to a smaller opening rather than a stem. These are often used in canning for transferring cooked food from a canning pot into wide-mouthed jars suitable for storage.
Buchner (BYOOCK-ner) funnels are one of three types of filtering funnels produced specifically for use in laboratories. They are available in white, glazed porcelain or lightweight polypropylene. Both types have large bowls dotted with holes (similar to a sieve) on the surface of a flat bottom over the stem. A rubber stopper with a stem-sized hole in it can be used to fit the funnel snugly into the opening of another container. (See References 1)
Stemmed and Stemless
Stemmed and stemless filtering funnels are made of laboratory glass and resemble standard kitchen funnels. They are constructed from borosilicate glass made to withstand “thermal shock and chemical attack better than most other kinds," according to the Indigo Instruments website. Stemmed funnels are shaped similar to a standard kitchen funnel and are used for gravity filtration. Stemless funnels are designed for hot filtrations, but can also be used for gravity filtration. (See References 1, 3, 5)
Separatory funnels are shaped like a bulb that gradually reduces down to a long, slender stem. They accept both rubber and ground glass stoppers at the opening, and have a glass or Teflon stopcock where the bulb meets the stem. Separatory funnels require the support of a ring stand. A stemmed glass filtering funnel is placed in the top of the separatory funnel to fill it. Then a test tube or other laboratory container can be placed under the stem of the separatory funnel to dispense precise amounts of liquid using the stopcock.