URINE S3 1 



The availability of the fermentation procedure as a quantitative 

 aid has been appreciably lowered through the important findings of 

 Neuberg and Associates. 1 They show that yeast has the property of 

 splitting of carbon dioxide from the carboxyl group of amino- and other 

 aliphatic acids. The active agent in this "sugar-free fermentation" is 

 an enzyme called carboxylase. Inasmuch as ammo-acids are always 

 present in the urine, the error from this source is apparent. 



7. Polariscopic Examination. Before subjecting urine to a polariscopic 

 examination the slightly acid fluid should be decolorized as thoroughly as possible 

 by the addition of a little lead acetate. The urine should be well stirred and then 

 filtered through a filter paper which has not been previously moistened. In this 

 way a perfectly clear and almost colorless liquid is obtained. 



In determining dextrose by means of the polariscope it should be borne in 

 mind that this carbohydrate is often accompanied by other optically active sub- 

 stances, such as proteins, fructose, /3-hydroxybutyric acid, and conjugate gly- 

 curonates which may introduce an error into the polariscopic reading ; the method 

 is, however, sufficiently accurate for practical purposes. 



For directions as to the manipulation of the polariscope see page 31. 



Below are given the specific rotations of some physiologically important sugars 

 as well as of certain other optically active substances the possible presence of 

 which must be borne in mind in determining glucose polarimetrically hi urine. 



Specific Rotation Specific Rotation 



Glucose +52.49 Fructose -92.25 



Maltose +136.5 /3-Hydroxybutyric -24.12 



Isomaltose +68.0 acid. 



Lactose +52.53 Conjugated Gly- Levorotatory in 



Pentose (i-ara- o.o curonic Acids. varying degrees, 



binose). 



Protein 



i. Scherer's Coagulation Method. The content of coagulable protein 

 may be accurately determined as follows : Place 50 c.c. of urine in a small beaker 

 and raise the temperature of the fluid to about 4OC. upon a water-bath. Add 

 dilute acetic acid, drop by drop, to the warm urine, to precipitate the protein which 

 will separate in a flocculent form. Care should be taken not to add too much 

 acid; ordinarily less than 20 drops is sufficient. The temperature of the water in 

 the water-bath should now be raised to the boiling-point and maintained there 

 for a few minutes in order to insure the complete coagulation of the protein pres- 

 ent. Now filter the urine 2 through a previously washed, dried, and weighed 



1 Xeuberg and Associates: Biochem. Zeitschr., vol. 31 and 36, 1911. 



2 If it is desired the precipitate may be filtered off on an un-weighed paper, and its nitrogen 

 content determined by the Kjeldahl method (see p. 483). In order to arrive at correct 

 figures for the protein content it is then simply necessary to multiply the total nitrogen 

 content by 6.25 (see p. 328). Correction should be made for the nitrogen content of the 

 filter paper used unless this factor is negligible. 



