Why do alterations in hydrogen ion concentrations occur in body fluids? What problems can they cause? What are the possible alterations for the concentrations of X3 potassium, calcium and magnesium ions in the blood? How much can they put the patient's life at risk? These questions are answered in a simple and clear and intuitive way by "Water and salt", a text that aims to provide a clinical interpretation method updated on the alterations of the acid-base balance, on hypo and hyper-natremia, on hypo and hypo-hyperkalemia (besides that of hypo and hyper-calcemia and hypo-magnesemia). The reader is accompanied in the interpretation of the various alterations of the acid-base balance, by the many clinical cases proposed, the true strength of the text. The authors propose not only an interpretative path, but also clear and concise indications on the therapeutic behavior to be adopted for the management of acid-base balance disorders and of hydro-electrolytic alterations.