Why mercury cure downwards and water cure upwards when placed in a glass tube?
Answers
As this picture shows, a meniscus can go up or down. It all depends on if the molecules of the liquid are more attracted to the outside material or to themselves. A concave meniscus, which is what you normally will see, occurs when the molecules of the liquid are attracted to those of the container. This occurs with water and a glass tube. A convex meniscus occurs when the molecules have a stronger attraction to each other than to the container, as with mercury and glass. A flat meniscus occurs with water in some types of plastic tubes; tubes made out of material that water does not stick to. In any case, you get the true volume of the liquid by reading the center of the liquid in the tube, which will the lowest vertical point of the liquid.
