Measuring the volume of a liquid with a graduated cylinder

Written By India Gate on Friday, May 27, 2011 | 1:44 AM

The surface of a liquid confined in a cylinder curves to form what is known as a meniscus. The meniscus of most liquids curves up the sides of the container, making the center of the curve appear lower than the edges. Mercury is one of very few exceptions - it curves down at the edges. Since reading the meniscus at the top or at the bottom of the curve will make a difference in the volume measured, it is generally agreed to always read the bottom of the curve. The smaller the container, the greater the curve of the meniscus. Pictured below is the meniscus in a 10 mL graduated cylinder. To gain experience in reading liquid volumes, click on the picture to enlarge it and read the volume in the following way: the meniscus in a graduated cylindar

1. The largest graduations on this graduated cylinder are numbered, representing milliliters. What whole number of milliliters are represented in the picture?
2. There are five graduations from one major line to the next in this picture. In other words, each milliliter is divided into tenths and each small graduation represents two tenths. What volume is represented in the picture, to the nearest tenth of a milliliter?
3. Both whole milliliters and tenths of milliliters can be read from the graduations in the picture. If divisions between the tenths graduations are estimated, the volume can be read to hundredths of a milliliter. What is the volume of liquid in the picture to the nearest hundredth of a milliliter?

As the diameter of the cylinder increases, the curve of the meniscus flattens out. See a picture of the meniscus in a 100 mL graduated to a local picture While the curve is not as pronounced, because of its thickness, we must still read the bottom of the meniscus. What volume of liquid is represented in the picture, to three significant digits?

You can see that the lines drawn on the answer pictures help identify the location of the bottom of the meniscus. If reading volumes in a cylinder is going to be regularly done, making a burette card link to a local picture might be worthwhile. This is a small index card with a very thick horizontal line drawn on it with a magic marker. By holding the card behind the cylinder, and immediately below the bottom of the meniscus, the volume can be easily read.