338 PHYSIOLOGICAL CHEMISTRY. 



EXPERIMENTS. 



1. Mucic Acid Test. Treat 100 c.c. of the urine under examin- 

 ation with 20 c.c. 1 of concentrated nitric acid and evaporate the 

 mixture in a broad, shallow glass vessel, upon a boiling water- 

 bath, until the volume of the solution is only -about 20 c.c. At 

 this point the fluid should be clear and a fine, white precipitate 

 of mucic acid should separate. If the percentage of galactose pres- 

 ent in the urine is low it may be necessary to cool the solution and 

 permit it to stand for some time before the precipitate will form. 

 It is impossible to differentiate between galactose and lactose by 

 means of this test, but the reaction does serve to differentiate these 

 two sugars from all other reducing sugars. A satisfactory differ- 

 entiation between galactose and lactose may be made by Bar feed's 

 test, p. 313. 



2. Tollens' Reaction. To equal volumes of the urine and hy- 

 drochloric acid (sp. gr. 1.09) add a little phloroglucin and heat the 

 mixture on a boiling water-bath. Galactose, pentose and glycur- 

 onic acid will be indicated by the appearance of a red color. Galac- 

 tose may be differentiated from the two latter substances in that 

 its solutions exhibit no absorption bands upon spectroscopical ex- 

 amination. 



LJEVULOSE. 



Diabetic urine frequently possesses the power of rotating the 

 plane of polarized light to the left, thus indicating the presence of 

 a Isevorotatory substance. This laevorotation is sometimes due to 

 the presence of laevulose, although not necessarily confined to this 

 carbohydrate, since conjugate glycuronates and /?-oxybutyric acid, 

 two other Isevorotatory bodies, are frequently found in the urine of 

 diabetics. Laevulose is invariably accompanied by dextrose in dia- 

 betic urine, but l&vuloswria has been observed as a separate anomaly. 

 The presence of Isevulose may be inferred when the percentage 

 of sugar, as determined by the titration method, is greater than the 

 percentage indicated by the polariscopic examination. 



EXPERIMENTS. 



i. Borchardt's Reaction. To about 5 c.c. of urine in a test- 

 tube add an equal volume of 25 per cent hydrochloric acid and a 

 few crystals of resorcin. Heat to boiling and after the production 



1 If the specific gravity of the urine is 1020 or over it is necessary to use 25-35 

 c.c. of nitric acid. Under these conditions the mixture should be evaporated 

 until the remaining volume is approximately equivalent to that of the nitric 

 acid added. 



