“…Estimated ordinary 24-hr. filtration and excretion of bicarbonate, free carbonic acid, and phosphate by man (From Sendroy, Seelig, and Van Slyke (33)) SUBSTANCE GLOMERULAR FILTRATE, 170 LITERS AT pH 7.4 URINE, 1.5 LITERS AT pH 6.1 Concentration Total amount Concentration Total amount The manner in which the kidney produces at will acid or alkaline urine may be deduced from experiments by Sendroy and Seelig (33), showing that bicarbonate is actively reabsorbed, although free carbonic acid is not. Bicarbonate concentration in the urine was found to vary from four times to one-twentieth of the bicarbonate concentration in the blood plasma.…”