How to Find the Volume of a Liquid Using a Graduated Cylinder

Finding the volume of a liquid is a crucial and basic task in almost all fields of hard science. Using a graduated cylinder is perhaps one of the most accurate ways of finding the volume of any given liquid. The structure and design of a graduated cylinder allows it greater accuracy in measuring volume than do other pieces of equipment, such as flasks, beakers, or regular test tubes. Therefore, learning how to use a graduated cylinder is a crucial step if you wish to have a future career in the sciences. This guide will therefore endeavor to teach you both the structure of the instrument and the correct procedure to find the volume of a liquid using a graduated cylinder.

Anatomy of a graduated cylinder

Before we begin learning how to use a graduated cylinder, it is important to know the basic parts of the instrument. If you really don't care, feel free to skip ahead to the next section. Graduated cylinders are roughly tubular pieces of lab equipment usually used to measure the volume of liquids. They are usually made of polypropylene. Polypropylene is very chemically resistant and will not shatter when dropped, making it ideal as a practical lab instrument. Along one side of most graduated cylinders you will usually find a series of vertically arranged gradient measurements. The top one of these will usually tell you the units of liquid that the graduated cylinder measures. Most classroom laboratory graduated cylinders measure the volume of liquid in milliliters.

How to find the volume of a liquid using a graduated cylinder

In order to find the volume of a liquid using a graduated cylinder you must first place the liquid inside of the cylinder. If you are handling liquids that are of an extreme temperature or of dangerous chemical content, be sure to wear protective lab gear. Once the liquid is inside, place the graduated cylinder on a level surface. Examine the surface of your liquid. You will notice that the surface of the liquid inside the graduated cylinder is not actually level, instead it appears to curve downward. This curve is called the meniscus. The meniscus occurs because of a complex process involving the polar sides of water molecules attracting to the sides of the cylinder. Therefore, in order to accurately find the volume of a liquid using a graduated cylinder, you must measure the liquid from the bottom of meniscus. Graduated cylinders are calibrated to provide a correct reading when used this way. Now simply identify the meter marking with which the bottom of the meniscus aligns. This is the volume of your liquid. When doing this be sure that your eyes are level with the meniscus: otherwise you will come away with an inaccurate measurement.

Tips and Hints

When learning how to use a graduated cylinder keep in mind that it is not the MOST accurate measurement. Depending on the volume of your liquid, and your level of vision, measurements can be as much as 10% off. There fore if greater accuracy is needed, consider using pipettes or burettes instead.