 Addition of acid gives soluble hydrolysis products, including the trimeric ion [Be3(OH)3(H2O)6]3+, which has OH groups bridging between pairs of beryllium ions making a 6-membered ring.At very low pH the aqua ion [Be(H2O)4]2+ is formed.Addition of hydroxide to Be(OH)2 gives the soluble tetrahydroxoberyllate/tetrahydroxidoberyllate anion, [Be(OH)4]2−.