P 2915 (OTTO) Praseodymium chloride, hydrate, 99.9% Cas 19423-77-9 - used in the motion picture industry for studio lighting and projector lights. P 2915 (OTTO) Praseodymium chloride, hydrate, 99.9% Cas 19423-77-9 - used to prepare insoluble praseodymium(III) compounds.