URINE 435 



excess the urine should be made alkaline and boiled in order to decom- 

 pose the ammonium salts. 



(c) Benedict's Test. 1 Benedict has modified the Fehling solution and has 

 succeeded in obtaining one which does not deteriorate upon long standing. 2 

 The following is the procedure for the detection of glucose in the urine : To 5 c.c. 

 of the reagent in a test-tube add 8 (not more) drops of the urine to be examined. 

 The fluid is then boiled vigorously for from one to two minutes and then allowed 

 to cool spontaneously. (Do not hasten cooling by immersion hi cold water.) 

 In the presence of glucose the entire body of the solution will be filled with a 

 colloidal precipitate, which may be red, yellow, or green hi color, depending 

 upon the amount of sugar present. In the presence of over 0.2-0.3 per cent 

 of glucose the precipitate will form quickly. If no glucose is present, the solution 

 will either remain perfectly clear, or will show a very faint turbidity, due to 

 precipitated urates. 



Even very small quantities of glucose in urine (o.i per cent) 

 yield precipitates of surprising bulk with this* reagent, and the positive 

 reaction for glucose is the filling of the entire body of the solution 

 with a precipitate, so that the solution becomes opaque. Since amount 

 rather than color of the precipitate is made the basis of this test, it 

 may be applied, even for the detection of small quantities of glucose, 

 as readily in artificial light as in daylight. Chloroform does not in- 

 terfere with this test nor do uric acid or creatinine interfere to such 

 an extent as in the case of Fehling's test. 



(d) Folin-McEllroy Test. 3 To 5 c.c. of the reagent 4 in a test tube add 5-8 

 drops of urine (never add more than 0.5 c.c.) and boil for 1-2 minutes or heat in a 

 beaker of boiling water for 3 minutes. If more than the normal traces of sugar 

 be present the hot solution will be filled with a colloidal (greenish-yellow or 

 reddish) precipitate as in Benedict's test. Because of the sensitiveness of this 

 test, when working with urine only a distinctly positive test obtained with the 

 solution still hot is to be regarded as positive. 



1 Benedict: Jour. Biol. Chem., 5, 485, 1909: Jour. Am. Med. Ass'n, 57, 1193, 1911. 



2 Benedict's new solution has the folio wing composition: 



Copper sulphate 17.3 gm. 



Sodium citrate 1 73 . o gm. 



Sodium carbonate (anhydrous) 100.0 gm 



Distilled water to 1000 . o c.c. 



With the aid of heat dissolve the sodium citrate and carbonate in about 800 c.c. of water 

 Pour (through a folded filter if necessary) into a glass graduate and make up to 850 c.c. 

 Dissolve the copper sulphate in about 100 c.c. of water. Pour the carbonate-citrate solu- 

 tion into a large beaker or casserole and add the copper sulphate solution slowly, with 

 constant stirring and make up to one liter. The mixed solution is ready for use, and does 

 not deteriorate upon long standing. 



3 Folin and McEllroy: Jour. Biol. Chem., 33, 513, 1918. 



4 Folin-McEllroy Reagent. Dissolve 100 g. of sodium pyrophosphate, 30 g. of diso- 

 dium phosphate and 50 g. of dry sodium carbonate in approximately i liter of water by 

 the aid of a little heat. Dissolve separately 13 g. of copper sulphate in about 200 c.c. of 

 water. Pour the copper sulphate solution into the phosphate-carbonate solution and 

 shake. 



