A synopsis of the work being done at the Preservation Services Division of tbe National Archives and Records Service. Magnesium hydroxide proved superior to magnesium carbonate as a starting material for magnesium bicarbonate. The pH of the solution is no indication of solution strength. Methods were developed for the determination of magnesium and of carbonate in papers that contain no interfering materials. Solutions of magnesium bicarbonate at 0.04 molar and weaker appear to be stable, especially if saturated with carbon dioxide and stored in closed containers.