STUDIES OF ACIDOSIS

Abstract

Calorimetric methods for the determination of urine pH have been described by Henderson and Palmer (l), Michaelis (2), and others, which are sufficiently accurate for most clinical purposes.Quagliariello and D'Agostino (3) proposed a calorimetric method, which checked their electrometric determinations with an error ranging from -0.16 to +0.15 pH.They employed phosphate buffers as standards, with neutral red and para-nit.rophenolindicators.The temperature was not controlled, nor was the dye concentration in the standard and unknown solutions uniform throughout the range of any one indicator.Apparently no attempt was made to prevent loss of CO2 from urine samples, or to take into consideration the partial pressure of this gas in the electrometric measurements.Marshall (4) has shown that the loss of COz from urine specimens may cause quite an appreciable error in pH determinations, amounting to several tenths of a pH in some alkaline samples.In the present paper we have attempted to increase the accuracy of the calorimetric method, and have controlled it by comparison with electrometric measurements.Due to reasons which will be pointed out, the accuracy of the method, even with the precautions employed, is only 0.1 pH as compared with an accuracy of f 0.02 pH in the case of blood determinations.The bicolor standards, used by Hastings and Sendroy (5) for blood plasma pH measurements, have been adapted to urine.