URINE. 311 



for the detection of dextrose in the urine : To five cubic centimeters 

 of the reagent in a test-tube add eight (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. In the 

 presence of dextrose the entire body of the solution will be filled 

 with a precipitate, which may be red, yellow or green in color, 

 depending upon the amount of sugar present. If no dextrose 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 dextrose in urine (o.i per cent) yield precipitates of 

 surprising bulk with this reagent, and the positive reaction for dex- 

 trose is the filling of the entire body of the solution with a precipi- 

 tate, 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 dextrose, 

 as readily in artificial light as in daylight. 



( d) Allen's Modification of Fehling's Test. The following pro- 

 cedure is recommended : " From 7 to 8 c.c. of the sample of urine 

 to be tested is heated to boiling in a test-tube, and, without separat- 

 ing arty precipitate of albumin which may be produced, 5 c.c. of 

 the solution of cupric sulphate used for preparing Fehling's solution 

 is added. This produces a precipitate containing uric acid, xanthine, 

 hypoxanthine, phosphates, etc. To render the precipitation complete, 

 however, it is desirable to add to the liquid, when partially cooled, 

 from i to 2 c.c. of a saturated solution of sodium acetate having 

 a feebly acid reaction to litmus. 1 The liquid is filtered and to the 

 filtrate, which will have a bluish-green color, 5 c.c. of the alkaline 

 tartrate mixture used for preparing Fehling's solution is added, 

 and the liquid boiled for 15-20 seconds. In the presence of more 

 than 0.25 per cent of sugar, separation of cuprous oxide occurs 

 before the boiling-point is reached; but with smaller quantities 

 precipitation takes place during the cooling of the solution, which 

 becomes greenish, opaque, and suddenly deposits cuprous oxide as 

 a fine brownish-red precipitate." 



(<?) Boettger's Test. To 5 c.c. of urine in a test-tube add i c.c. 



'Sufficient acetic acid should be added to the sodium acetate solution to render 

 it feebly acid to litmus. A saturated solution of sodium acetate keeps well, but 

 weaker solutions are apt to become mouldy, and then possess the power of 

 reducing Fehling's solution. Hence it is essential in all cases of importance to 

 make a blank test by mixing equal measures of cupric sulphate solution, 

 alkaline tartrate solution and water, adding a little sodium acetate solution, 

 and heating the mixture to boiling. 



