Na+ concentration, measured by the flame photometer, cryoscopic osmolality, and the specific electrolyte conductivity of urine show a close statistical correlation if only small amounts of a molecular disperse solution are dissolved in the urine. 2. Since conductance of a fluid is an expression of its ion concentration, better relationships exist between Na+ concentration and conductivity than between Na+ concentration and osmolality. 3. In the presence of large amounts of glucose in the urine, osmolality no longer represents the electrolyte content, and therefore no longer serves as a parameter of renal concentration power. On the other hand, the close correlation between conductance and Na+ concentration remains. 4. Conductometry supplements osmometry significantly by its selective capacity to determine electrolyte components in the urine. 5. Owing to the short time spent on the method and small errors in technique, it remains debatable whether conductometry is preferable to osmometry in normal cases for determining measurements in concentration in the urine.
