Caustic soda is a strong alkali used in the pulping process to dissolve lignin and other impurities, separating the cellulose fibres. This process effectively "degums" or cleans the fibres before they are processed into paper. Bleaching powder is used for whitening the pulp after pulping. Sulphuric acid and nitric acid are strong acids with different applications (e.g., in chemical processing or nitration) and are not typically the primary agents for degumming in standard paper pulping, although acidic processes (like the sulfite process) exist, they target lignin and hemicellulose differently than the general removal of gummy substances often associated with alkaline treatments or specific fibre degumming steps.