Nitrobenzene is an organic liquid which consists of a benzene ring with a nitro (NO2) group attached to one of the carbons instead of a hydrogen. In can be used in organic chemistry as a solvent. A dry sample of most any organic solvent can be obtained by using a drying agent. A drying agent is an inorganic solid with a large surface area that absorbs water but does not itself dissolve in organic solvent. The two most commonly used drying agents are magnesium sulfate (MgSO4) and sodium sulfate (Na2SO4). Add some of the drying agent to a sample of nitrobenzene and let it sit for several minutes to absorb any water present. Then simply filter off the drying agent by pouring the mixture through some filter paper and let the dry nitrobenzene drain into a fresh, dry flask or bottle for storage.