Sodium urate is 15 times more soluble than
uric acid. When pH equals pKa (5.8),
uric acid and sodium urate are present in equal quantities. As pH increases, the ratio of sodium urate to uric acid increases. At a pH of 6.8, 10 times more sodium urate is present than uric acid; whereas, at a pH of 7.8, 100 times more sodium urate is present than uric acid"
www.emedicine.com/ped/topic2361.