What material forms an "upside down", "reverse", or "convex" meniscus?

The formation of a meniscus in a liquid refers to the curvature of the liquid's surface in response to its interaction with the container and the forces of cohesion and adhesion. Mercury is unique when it comes to its meniscus due to its high surface tension and cohesive properties.

Mercury does not adhere well to most materials, meaning it does not cling to the sides of the container. Instead, it creates a "reverse" or "convex" meniscus, which appears to bulge upward in the center when viewed from the side. This contrasts with water and many other liquids that typically exhibit a concave meniscus, where the liquid curves downward at the edges because adhesive forces between the water molecules and the container's surface are greater than the cohesive forces among the water molecules themselves.

In summary, the characteristic of mercury forming an "upside down," "reverse," or "convex" meniscus is rooted in its properties of high surface tension and lower adhesive interactions with container materials compared to cohesive interactions among mercury atoms. This results in the distinctive shape that makes mercury's meniscus stand out from those of other liquids.