METHODS FOR THE DIRECT QUANTITATIVE DETERMINATION OF SODIUM, POTASSIUM, CALCIUM, AND MAGNESIUM IN URINE AND STOOLS

Abstract

In the study of the inorganic metabolism of children it is frequently necessary to perform a large number of determinations of the various inorganic elements in urine and stools.The question of the amount of material available and the time required for a given determination becomes an important consideration.We have elsewhere reported simple methods for the quantitative estimation of sodium, potassium, calcium, and magnesium in serum (1, 2, and 3).It has been found possible to modify the sodium, potassium, and calcium methods so as to make them applicable to the acid extract of the partly ashed residue of urine and stools.For the determination of magnesium in urine and stools we have used the principle of alkalimetric titration of ammonium magnesium phosphate first suggested by Stolba (4).This procedure was subsequently modified by Mohr ( 5) and Kraus (6).Recently the same principle has been used by Bauzil(7), Angiolani (8), and Fiske (9) for the estimation of inorganic phosphates in urine.By the use of the methods described below a considerable saving in time and material is effected.The degree of accuracy of these methods is indicated in the tables. Preparation of Material.Xtoob.-The fresh stool for a measured period is collected in a weighed porcelain dish.This is heated on the water bath until dry.95 per cent alcohol is added and evaporated.This latter procedure is repeated, making two additions of alcohol in all.After thorough drying over the water bath the dish and contents 1