Quantitative determination of urine sodium by means of ion exchange resins.

The method for quantitative determination of serum sodium as described by Vanatta and Cox (1) is adaptable to determination of urine sodium. However, wider variations in sodium and potassium concentrations, and the presence of ammonia and other interfering substances, necessitate certain modifications of the procedure. Apparatus and Reagents-The items of apparatus needed for the determination of urine sodium are those required for determination of serum sodium with the following additions and exceptions. 1. The 50 cm. column of resin with a cross-sectional area of 0.93 to 1.04 sq. cm. is increased to a length of 55 cm., the diameter remaining the same. A 50 cc. burette is adequate for either column. 2. A 250 cc. Erlenmeyer flask. 3. A small glass boiling bulb which will fit the opening of the 250 cc. Erlenmeyer flask. 4. A stopper with a CO2 absorption tube in it which will fit the 250 cc. Erlenmeyer flask. The same reagents as for determination of serum sodium are required, with the addition of the following reagents: 1. Nitrogen gas under pressure or compressed air washed in alkali or passed through soda lime. 2. 100 cc. of toluene with two or three crystals of thymol. 3. Soda lime or a similar CO2 absorber.