The Estimation of Chlorides in Blood

Renewed interest in blood chlorides has been aroused by Allen,’ who has endeavored to show that salt retention is the cause of pure hypertension, and also of the hypertension in many cases of kidney disease. The estimation of this constituent has been most often conducted on the plasma, rather than on whole blood, but there would now appear to be some question as to the reliability of plasma analysis in this connection unless the plasma is immediately separated from the corpuscles. In any case a significant change in the blood chlorides should definitely affect the chloride content of whole blood as well as that of the blood plasma. The practical use of various laboratory tests of diagnostic import has ordinarily kept pace with their reliability and simplicity. That the estimation of the blood chlorides has not received more clinical consideration must be ascribed either to lack of appreciation of the possible value of the test, or to the difficulties in technique. A method of chloride estimation is described below which we believe contributes to the simplicity and rapidity of the test, without impairing its accuracy. Most American workers who have studied this question have ,employed the iodimet,ric method of McLean and Van Slyl~e,2 or some modification of it. With their original method the blood proteins were removed with the aid of heat, acetic acid, magnesium sulfate, and blood-charcoal. The chlorides were then precipitated in acid solution with silver nitrate and the excess was titrated with iodine, using starch as an indicator. Owing t.o