The graduated cylinder is a tall, thin container used to measure the volume of liquids. It is a very common piece of laboratory equipment. Chemists use graduated cylinders just as you would use measuring cups in your kitchen.
A graduated cylinder is a tube that is sealed at one end and open at the other end. It has a calibrated volumetric scale etched or marked on the outside. The cylinder has a large base on the bottom for stability and a lip on the top edge for pouring. The cylinder may also come equipped with a plastic "bumper guard" to prevent breakage if knocked over. Graduated cylinders come in a range of sizes (volumetric capacity) ranging from 10 milliliters to 4 liters.
Graduated cylinders are made of either plastic or glass. Glass cylinders are clear, easy-to-read and resistant to most chemicals. In addition, glass cylinders are heat-resistant and can be heat-sterilized. However, glass cylinders are easily broken. This is especially problematic for graduated cylinders because their elongated shape makes them easy to knock over and shatter. Plastic cylinders are unbreakable, but some chemicals attack the plastic and fog the surface of the cylinder, making it difficult to read. The choice between plastic and glass will depend upon the expected use.
To measure fluid volume, carefully pour the liquid into the graduated cylinder. Hold the cylinder up so that the liquid line is at eye level. Make sure that the cylinder is hanging straight up and down. The surface of most liquids will curve upward along the side of the cylinder. This characteristic is known as the "meniscus" and is caused by the attraction of liquid molecules to the cylinder's surface. The scale on the outside of the cylinder is read like a ruler. The graduated cylinder measurement closest to the bottom of the meniscus is the correct fluid volume measurement.
Graduated cylinders are found in virtually every laboratory. Chemists use them to measure reagents and analytical samples. You will see graduated cylinders in school chemistry labs, analytical laboratories and research labs. Graduated cylinders are used to measure liquids in food manufacturing plants and photography darkrooms. Graduated cylinders are even included in many chemistry sets.
The accuracy of a graduated cylinder depends upon its size. For example, a 10-milliliter cylinder has 1/10-milliliter divisions while a 100-milliliter cylinder has one-milliliter divisions. Reading the scale is technique-dependent and subject to human error. As a measuring device, the graduated cylinder is more accurate than a beaker or flask, but less accurate than equipment such as a pipet or buret.
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