Copper(II) nitrate trihydrate → Cupric nitrate

Five Hundred and seventy grams of Cu(NO3)2.2.5H2O (typically designated as copper (II) nitrate trihydrate) was dissolved in water and diluted to 2.0 liters to give 1.25 molar copper nitrate solution. An 18% sodium hydroxide solution was prepared by dissolving 2.5 grams sodium hydroxide in water and diluting to 1.0 liter. The caustic solution was allowed to cool to room temperature before using in the reaction that follows. Sodium bicarbonate, 8.4 grams, 0.1 mole, was added to a three liter reactor and was dissolved in 0.25 liter of water to allow for agitation. The pH of the bicarbonate solution was raised to 11.5 with sodium hydroxide. (This prevents carbon dioxide formation on addition of the relatively acidic cupric nitrate solution due to lowering the pH below about 6). The aqueous carbonate medium is agitated and an aliquot of the copper nitrate solution (80.1 ml, 0.1 moles) is added. The resulting intermediate which forms immediately is then converted to the hydroxide by the addition of approximately 37 ml of the above caustic solution. After sixteen cupric nitrate-sodium hydroxide cycles the temperature of the slurry had reached 32° C. with a pH of 10.1 The solution was then filtered under vacuum conditions and washed with water. The copper assay was 56.59% after drying for five hours at 65° C. The copper was recovered quantitatively.