We are beginning to use phosphoric acid in dissolution of silicates, and are concerned about blank problems. Ultra-pure phosphoric is pretty expensive, so we were wondering if anyone knows a way to clean up reagent grade phosphoric acid through distillation or otherwise. We already use two-bottle teflon stills for other mineral acids, but we have no experience with phosphoric. Thanks for any info. --Andy ______________________________________________________________________________ Andrew Kurtz Department of Geological Sciences Snee Hall, Cornell University Ithaca, NY 14853 phone: (607) 255-9608 fax: (607) 254-4780 email: [log in to unmask] ______________________________________________________________________________