Methanol → Gluconic Acid

Hydrated hafnium-ammonium-gluconate was prepared as follows: 125 grams of hafnium oxychloride.8H2O was dissolved in 600 ml of 50% aqueous solution gluconic acid. Four litters of anhydrous methanol were added to precipitate the hafnium-gluconate and the suspension was heated to 60° with stirring for 30 minutes. The pH of the preparation was then adjusted to 6.5 by addition of concentrated NH4OH. The hot solution was filtered to remove NH4Cl and ammonium gluconate. The precipitate was dried at 90° for 1 hour, resuspended in anhydrous methanol at 60° with stirring for 60 minutes then filtered to remove additional excess of NH4Cl and ammonium-gluconate. The precipitate was further extracted to remove additional NH4Cl and ammonium-gluconate employing anhydrous methanol in a Soxhlet apparatus, extraction was continued until the methanol surrounding the precipitate was clear. The precipitate was then dried at 90° for approximately 2 hours and ground to a fine powder. Elemental analysis was consistent with a formula of (HfO)2 (NH 4)2 gluconate3 (H2O)x. It was found that the same final product was obtained when the molar ratio of gluconic acid to hafnium was varied from 1:1 to 100:1. Moreover, the same product was obtained utilizing hafnium-tetrachloride instead of hafnium-oxychloride.