The means of measuring the humidity of the atmosphere are called hygrometers.

The conversion of ferric chloride (FeCl₃) to ferrous chloride (FeCl₂) is not specifically called "degradation." Instead, it is a type of chemical reaction known as a reduction reaction. In this process, ferric chloride (FeCl₃), which contains iron in the +3 oxidation state, gains electrons and is reduced to ferrous chloride (FeCl₂), where iron is in the +2 oxidation state. The reduction reaction involves the gain of electrons, leading to a decrease in the oxidation state of iron.