Products Obtained by Heating Mixtures of Sodium Dihydrogen Phosphate and Boric Acid

Abstract

Various kinds of reaction products were obtained on dehydration of mixtures of NaH2PO4 2H20 and H3B03 with various mole ratios by heating at 400-750° C. The products were. subjected to chemical analyses, IR spectrophotometric measurements and DTA. When a mixture of 3 moles of NaH2PO4 2H20 and 2 moles of H3B03 was heated at 400-400° C, a new compound containing macromolecular chains with a skeleton of B-O-P linkages was considered to be formed; the obtained compound was light, finely-divided and sparingly soluble powder and its mp was about 700° C. When initial mixtures had a mole ratios of NaH2P04.2H20 to H3B02 other than that of 3: 2, the reaction products consisted of some complicated polymers characterized by the formation of B-O-P linkages. In the cases of the glassy products with n value of 9-18, their water-soluble parts showed the ortho- pyro-: tri-: high polymeric phosphoric acid ratio (in P205) to be 1: 4: 2: 2 (n-6); here, n refers to a mole number of NaH2PO4.2H20 mixed with 2 moles of H3B03. The addition of a small amount of H3B03 to NaH2PO4.2H20 showed the tendency that the thermal conversion of NaP03-(II) into Na3(P03)3 was appreciably prevented.