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RESULTSRepresentative recoveries from tissues and urine are given in Tables I and 11. The recoveries were done on pooled urine and blood specimens which did not contain demonstrable quantities of mercury. It will be noted that recoveries are obtainable with an error of less than 2 micrograms. The working curve is of sufficient size to permit reading 0.25 microgram and no attempt was inadr to rst,imate smaller quantities. Table 11. Recoveries of Known Quantities of ?Zercury from 100 MI. of Urine Mercury hlercury rldded Recoyered Error Mzcrograms Mtcrograms Mtcrogram. 2.5 5.0 5.0 10.0 10.0 . 20.0 30.0 40.0 50.0 100.0 4.50 7.00 6.75 11.50 11.75 21.50 31.25 42.25 51.00 100.00 Reagent blank contained 1.75 micrograms of mercury. +0.25 + 0 . 2 5 0 00 -0 25 0.00 -0.25 -0.50 +0.50 -0.75 -1.75 ACKNOWLEDGMEhTThe author is indebted to Elmrr F. Kluchrsky for aiding in the early part of this Lyork.' abscissa axis. The curve it: constructed on a basis of concentration of mercury per 25 ml. However, increased sensitivity can he obtained by employing a smaller volume of dithizone. The values for the construction of the curve were obtained by extracting known amounts of mercury under conditions similar to those described in the procedure. The standard mercury solution was prepared by dissolving 10 grams of metallic mercury in approximately 200 ml. of nitric acid and then diluting to 1 liter. Subsequent dilutions of this standard were made so that 1 ml. contained 5 micrograms of mercury.Munson-Walker cuprous oxide reducing values of L-xylose are markedly lower than are those of D-xylose. Similar differences were noted in the case of L-and D-galactose. This indicates an asymmetric oxidation of the enantiomorphs as reported by Richtmyer and Hudson. The yeast Saccharomyces carlsbergensis, which ferments D-galactose quantitatitely, is without effect on L-galactose, thus permitting a differential fermentation of the former. The yeast Hansenula suaveoEens (N.R.R.L. 838), which quantitatively ferments n-xylose, is without action on either L-xylose or L-galactose. (4) show.ed that the 1)-m t i L-I forms of altrose, when oxidizrd with alkaline ferricyanide or a copper tartrate solution prepared from mesoor dl-tartaric acid, showed no difference in reducing power. Similar results were obtained with D-and L-arabinose. On the other hand, the relative reducing powers of the enantiomorphs towards optically active reagents-e.g., an alkaline copper tartrate prepared from tltartaric acid-were markedly different. This indicated that such optically active reagents caused an asymmetric oxidation of the D-and L-forms of these sugars, and the enantiomorphs could be differentiated sharply by their reducing action towards such reagents. K 1936 Richtmyer and HudsonExperiments have shown that this same type of asymmetric olidation applies, respectively, to D-and L-galactose and D-and L-xylose, and that it may be measured conveniently by means of the ordinary llunson-Walker determination. Furthermore, the enantiomorphs may be differentiated quantitatively by...

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