Which part of the meniscus is the most accurate measure of liquid volume?

This curve is known as a meniscus. Volumetric glassware is calibrated such that reading the bottom of the meniscus, when it is viewed at eye level, will give accurate results. Viewing the meniscus at any other angle will give inaccurate results.

Why do we use the bottom of the meniscus?

The meniscus make accurate reading of the level very difficult but it only affects the surface near the sides of the container. The bulk of the surface is away from the sides so reading the level from the bottom minimises the likely error. It’s measured at the bottom by convention.

Do you read from the bottom of the meniscus?

You must get at eye-level with the meniscus to obtain an accurate reading. Pick up the glassware to bring it up to eye level or bend down to take a measurement. E.g. with a concave meniscus, measure the bottom of the meniscus and for convex meniscus, take the reading from the top of the meniscus.

When measuring liquid volume you should measure the lower meniscus?

Measure so that the line you are reading is even with the center of the meniscus. For water and most liquids, this is the bottom of the meniscus. For mercury, take the measurement from the top of the meniscus.

What is the bottom of the meniscus?

Reading a Meniscus For a concave meniscus, the volume of the liquid in the container is read from the bottom of the curve. You may notice a ‘line’ of liquid at the very top, forming the curve itself. The bottom of the curve is the lower side of this line.

How do you read a meniscus on different liquids?

If the meniscus is a concave meniscus, read at the lowest level of the curve. If the meniscus is convex, take your measurement at the highest point of the curve. The short answer: Take your measurement from the center of the meniscus. It’s that easy.

Which meniscus should be read for colored liquids?

During lab experiments especially in chemistry, we are always told to take a reading at bottom of the meniscus for colourless liquids and the upper meniscus of coloured liquids.

Why is it necessary that the eye should be at the same level as the bottom of the meniscus when reading the level of the liquid in a graduated cylinder?

Your eye must be on the same level as the bottom of the meniscus to read the volume correctly. The meniscus formed by a non-wetting liquid, such as mercury (Hg), is convex with the highest point in the center. In the case of a convex meniscus, the highest point is used to make the reading.

Why do we need to read the lower meniscus and not the upper meniscus?

Lesson Summary A meniscus occurs because of surface tension in the liquid and must be read at eye level. For a concave meniscus, the correct volume will be read at the bottom of the curve. For a convex meniscus, the opposite is true and the correct reading will be at the top of the curve.

What property of water causes meniscus?

Adhesion is responsible for a meniscus and this has to do in part with water’s fairly high surface tension. Water molecules are attracted to the molecules in the wall of the glass beaker.

When measuring volume which is the most accurate?

Volumetric flasks, burettes, and pipettes made for measuring small amounts of liquid are the most accurate, with tolerances of less than ±0.02.

When measuring liquid samples when will you use the lower meniscus upper meniscus?

If the meniscus is convex, take your measurement at the highest point of the curve. The long answer: To read a meniscus, you first need to see what type of meniscus your liquid forms. If the meniscus is a concave meniscus, read at the lowest level of the curve.

How do you measure liquid from the meniscus?

For water and most liquids, this is the bottom of the meniscus. For mercury, take the measurement from the top of the meniscus. In either case, you are measuring based on the center of the meniscus. For a flat meniscus, make sure the liquid is level.

Why lower meniscus is not visible in colourless solution?

This is due to the reason that in case of coloured solutions lower meniscus is not visible clearly. In the case of colourless liquid, it is easy to observe the phase boundary, whether it is convex or concave hence in the colourless liquid lower meniscus may be considered.

When to use the upper or lower meniscus of a Pipet?

All pipets are calibrated to the lower meniscus, so use it as long as you can see it. If the solution is very dark or opaque to the extent that the lower meniscus is not visible, only then use the upper meniscus. In the case of liquids like mercury that form a convex meniscus, use the top of the convex meniscus.

Why is it important to account for the meniscus?

This makes taking measurements easy. When you read a scale on the side of a container with a meniscus, such as a graduated cylinder or volumetric flask, it’s important that the measurement accounts for the meniscus. Measure so that the line you are reading is even with the center of the meniscus.