An apparatus for adjusting a stream of air to definite relative humidities using saturated salt solutions and the application of this equipment to the determination of hygroscopic moisture in grains is described. Data are presented to show that under equilibrium conditions sunflower hulls have a higher moisture content than meats. For oats this condition is reversed. In the lower humidity ranges sunflower and oat hulls show similar moisture contents, which fall about 2% below the values for wheat, oat groats, flax, and sunflower meats computed to an oil-free basis. It is concluded that hygroscopic equilibria in grains are governed more by the structure of the grain and physical absorption phenomena than by the chemical components.