ABSTRACT
Sodium chloride is the principal solid of sea water. These ions, sodium and chloride, are also the chief ions of the extracellular fluid of the human body. Ordinarily, there is a very active intake of both sodium and chloride and a corresponding urinary excretion of the salt. The excretion of salt and the excretion of water from the human body are intimately interrelated so that the concentrations of both sodium and chloride in the serum are maintained in quite a constant manner. Salt was identified as an important constituent of blood by Robert Boyle during the 17th century. Sodium methods involving chemical reactions, such as uranyl acetate precipitation procedures with subsequent colorimetric measurement, are not widely used anymore. One of the major limitations in the measurement of urine sodium is that the measurement requires a clinical laboratory equipped with some form of special instrumentation.
