Laboratory Glassware: Types of Laboratory Tubes
Scientific laboratories use a panoply of equipment to store materials and conduct research and experiments; this includes a variety of tubes used for storing, mixing, heating and cooling chemicals, each with specialized designs.
- A boiling tube is a thick cylindrical alternative test tube primarily used for boiling chemical solutions. It is thicker and longer than a standard test tube, which it resembles, so that liquid doesn’t boil over. The entire tube can be immersed in a Bunsen burner flame because it is composed of borosilicate glass, which is resistant to thermal shock and will not crack when exposed to extreme heat.
- Centrifuge tubes are used in laboratory centrifuges, machines that spin samples in order to separate solids out of liquid chemical solutions. The centrifuge tubes can be made of glass or plastic, and resemble miniature test tubes with tapered tips. The design of the taper varies depending on the types of solids—biomolecules, insolubules, etc.—within the chemical sample. Centrifuge tubes, also called centrifuge tips, are placed within the centrifuge and spun at very high velocity for a set amount of time. Once the time is up, a scientist or lab technician removes the tube and pours the leftover liquid, the supernatant, into another container, leaving the solid, or precipitate, available for other uses.
- NMR tubes are used exclusively in nuclear magnetic resonance (NMR) spectroscopy, a type of imaging that can be performed on solid-state molecules. NMR tubes are thin-walled, cylindrical tubes designed to contain NMR spectroscopy samples, so they are usually only 5 mm in diameter. Instead of a rubber or cork plug or cap, NMR tubes generally seal with polyethylene caps, or by melting the glass at the open end and then cracking it in a twist.
- Test tubes are extremely common thin-walled cylindrical tubes that can be used for holding chemical solutions. Scientists use test tubes as containers for liquid chemical solutions, mixing, heating or cooling, producing cultures, and other applications. Because test tubes have rounded bottoms, they cannot stand on their own, and require a test tube stand or some other device to hold them upright.
- Thiele tubes are handblown tubes shaped in a triangular fashion, resembling a test tube that then loops back upon itself. They are typically used to determine the boiling points or melting points of different chemicals. A Bunsen burner heats the handle of the filled Thiele tube, which causes a convection current to loop around the handle, down the test tube portion, and then back up the handle. To determine the boiling point, a small capillary is placed within the sample and the tube is sealed and heated. Once the sample begins to boil, heating stops. The temperature at which the capillary sucks in the liquid sample is the exact temperature of the boiling point. The melting point can be observed by attaching a thermometer to the inside of the tube and heating a substance until it melts.
- Thistle tubes are tubes designed to allow chemists to add material through a semi-permeable membrane or specially designed stopper. They have long stems that end in a reservoir bulb with a flared rim. Thistle tubes are specifically designed to fit in complementary stoppers on Erlenmeyer and other flasks, so that new materials can be introduced to other compositions.
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