Acid-Base Balance The amount of H+in a solution is expressed as pH. 。pH=-log[Ht] Increasing [H+],increases acidity. Increasing [OH-]increases alkalinity. Most organisms grow best between pH 6.5 and 8.5. • The amount of H+ in a solution is expressed as pH. • pH = −log[H+] • Increasing [H+], increases acidity. • Increasing [OH− ] increases alkalinity. • Most organisms grow best between pH 6.5 and 8.5. Acid-Base Balance