ESTIMATION OF SUGAR IN URINE. 813 



chloric acid or sulphuric acid, The activity of the yeast must, when 

 necessary, be controlled by a special test. Place 200 cc. of the urine 

 in a 400 cc. flask, add a piece of compressed yeast the size of a pea, and 

 subdivide the yeast through the liquid by shaking; close the flask with 

 a stopper provided with a finely-drawn-out glass tube, and allow the test 

 to stand at the temperature of the room or, still better, at 30-35 C. 

 After twenty-four hours the fermentation is ordinarily ended, but this 

 must be verified by the bismuth test. After complete fermentation filter 

 through a dry filter, bring the filtrate, to the proper temperature, and 

 determine the specific gravity. 



If the specific gravity be determined with a good pycnometer sup- 

 plied with a thermometer and an expansion-tube, this method, when the 

 quantity of sugar is not less than 0.4-0.5 per cent, gives, according to 

 WoRM-MtiLLER, very exact results, but this has been disputed by BuDDE. 1 

 For the physician the method in this form is not serviceable. Even when 

 the specific gravity is determined by a delicate urinometer which can 

 give the density to the fourth decimal, exact results are not obtained, 

 because of the ordinary errors of the method (BUDDE); but the errors 

 are usually smaller than those which occur in titrations made by unskilled 

 hands. 



When the quantity of sugar is less than 1.5 per cent, these methods 

 cannot be used. Such small amounts cannot, as already mentioned, 

 be determined by titration directly, because of the reducing power of nor- 

 mal urine. In such cases, it is better to first determine the reducing power 

 of the urine by titration according to BANG or KNAPP, then ferment the 

 urine with the addition of yeast and titrate again. The difference 

 found between the two titrations calculated as sugar gives the true 

 quantity of the latter. 



The determination of the sugar by fermentation can be so performed 

 that the loss in weight due to the C02 can be estimated, or the volume 

 of the gas measured. For this last purpose LOHNSTEIN 2 has constructed 

 a special fermentation saccharometer, and his " precision saccharometer " 

 is to be recommended. Based upon LOHNSTEIN'S instrument, WAG- 

 NER 3 has constructed a "fermentation saccharo-manometer," which 

 has certain advantages over LOHNSTEIN'S apparatus. 



ESTIMATIONS OF SUGAR BY POLARIZATION. In this method the 

 urine must be clear, not too deeply colored, and, above all, must not 

 contain any other optically active substances besides glucose. The 

 urine may contain several levorotatory substances such as proteids, 

 /3-oxy butyric acid, conjugated glucuronic acids, the so-called LEO'S sugar 

 and less often cystine, all of which are unfermentable. The proteid is 

 removed by coagulation, and the others are detected by the polariscope 

 after complete fermentation. The fermentable fructose is detected in a 

 special manner (see below), and the dextrorotatory milk-sugar differs 

 from glucose in its not fermenting readily. By using a delicate instru- 



1 Roberts, The Lancet, 1862; Worm-Muller, Pfliiger's Arch., 33 and 37; Budde, 

 ibid., 40, and Zeitschr. f. physiol. Chem., 13. See Lohnstein, Pfliiger's Arch., 62. 



2 Berlin, klin. Wochenschr., 35, and Allg. med. Central-Ztg., 1899; Goldman, Chem. 

 entralbl., 1907, 1, 1149. 



3 Munch, rned. Wochensch., 1905. 



