Examination of the urine; a manual for students and practitioners . heatedtoo much the color becomes brown, like cafe au lait, and isno longer characteristic. Milk-sugar gives a yellow-red tobrown color (Sahli). This test is too intricate for routinework. Glycuronic acid compounds may give a similarreaction, but with this exception Rubners test is one of themost reliable we,have. Phenylhydrazin Test.—This test should be employedwhenever there is doubt whether the reduction of copperor bismuth is due to the presence of glucose (or some othercarbohydrate) or to the presence of creatinin, uric ac
Examination of the urine; a manual for students and practitioners . heatedtoo much the color becomes brown, like cafe au lait, and isno longer characteristic. Milk-sugar gives a yellow-red tobrown color (Sahli). This test is too intricate for routinework. Glycuronic acid compounds may give a similarreaction, but with this exception Rubners test is one of themost reliable we,have. Phenylhydrazin Test.—This test should be employedwhenever there is doubt whether the reduction of copperor bismuth is due to the presence of glucose (or some othercarbohydrate) or to the presence of creatinin, uric acid,hippuric acid, etc., in excess. It is based upon the principlethat with glucose present in per cent, or even smalleramounts, phenyl glucosazon (C18H22N404) is formed bythis method, a compound which crystallizes in character-istic yellow needles recognizable under the microscope,and usually arranged in sunburst fashion (Plate 3).These crystals (glucosazon) are almost insoluble in water,but soluble in boiling alcohol and melt at 204 ° C. Similar Plate 3. Crystals of Phenylglucosazone {after von jaksch). DETECTION OF SUGAR IN THE URINE IO9 compounds are formed with this method in the presence oflactose (galacosazon), levulose (levosazon), the pentoses(pentosazon), and glycuronic acid, but these differ in theirmelting-points or in other respects as shown in the fol-lowing table (Zunz, quoted by Emerson): I. Gives crys-tals of phe-nylhydrazin -jin urine itself. r (a) Fermenta- f 1. Dextrorotatory=Glucose. A. Melting-point I tion positive. ( 2. Levorotatory = crystals about i (j) Fermenta-2°°° C* [ tion negative Lactose. B. Melting-point f («) Orcinreac- of crystals about \ tlon Positive Pentoses. 1500 C [ (b) Orcin reac- t tion negative Isomaltose. II. Gives crystals with phenylhydrazin only after urine has been J >curonictreated by heating with dilute H0SO4. 1 pounds0™ Method of Testing with Phenylhydrazin.—Into a gm. of the colorless cry
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