The mercury combining power of deproteinized blood.

Abstract

In the study of renal function, simple methods that give clinically accurate data are desirable, particularly to the physician to whom the more complicated blood analyses are not available. The salivary urea index, recently described, 1 is such a method. This test is based on the principle that urea is present in the saliva in definite concentrations depending on the amount in the blood. The salivary urea increases with urea retention in the body. The degree of urea retention can be estimated clinically by the simple measurement of the mercury combining power of the saliva quite as satisfactorily as by the more elaborate blood urea determination.

Since our study of the mercury combining power of saliva and the development of the salivary urea index, we have modified the technic so that the same simple test may be applied directly to the blood. An index of the non-protein nitrogen and the urea of the blood is thus easily and quite rapidly available.

TECHNIC.

To 10 per cent trichloroacetic acid in a centrifuge tube is added an equal amount of oxylated whole blood, preferably 5 cc. of each, and this is centrifuged for four to five minutes. If a centrifuge is not available, the mixture may be filtered, but it may be necessary to use 6 or 7 cc. of blood to obtain sufficient filtrate for the test. On this protein-free filtrate (preferably 5 cc.) is performed the test for the mercury combining power with 5 per cent mercuric chlorid, identically as described for the estimation of the salivary urea index. That is, to the filtrate is added by titration 5 per cent mercuric chlorid until there is a slight excess, as indicated by the appearance of the first faint tinge of brown within three seconds when a test drop is added to a drop of saturated sodium carbonate on a spot-plate.