ABSTRACT
Water and water vapor can be found everywhere. Because of the asymmetrical distribution of their electric charge, water molecules are easily adsorbed on almost any surface, where they are present as a mono-or multimolecular layer of molecules. Stored foodstuffs or raw materials may dry up at low humidity or get moldy at high humidity. In many industrial processes, the measurement of moisture and humidity is important for the maintenance of the optimum conditions in manufacturing. In average environmental conditions, water can also be present in the liquid and solid phase, the reason to speak of water vapor rather than of water gas. The gravimetric method is the most fundamental way of accessing the amount of water vapor in a moist gas. In a gravimetric hygrometer, the water vapor is frozen out by a cold trap or absorbed by a chemical desiccant and weighed, while the volume or the mass of dry gas is measured directly.
