URINE 419 



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) Haines' Test. This is a copper reduction test similar in many 

 respects to the Fehling and Benedict reactions. In Haines' solution 1 

 the cupric hydroxide is held in solution by glycerol instead of Rochelle 

 salt as in Fehling's solution. 



Perform the test as follows : Introduce about 5 c.c. of Haines' solution 1 into a 

 test-tube and heat to boiling. If no reduction occurs add 6-8 drops of the urine 

 and again bring to a boil. If glucose is present an abundant yellow (cuprous 

 hydroxide) or brownish-red (cuprous oxide) precipitate is thrown down. This 

 test is about as delicate as Fehling's test. 



(e) Allen's Modification of Fehling's Test. The following procedure is recom- 

 mended: "From 7 to 8 c.c. of the sample of urine to be tested is heated to boiling 

 in a test-tube, and, without separating any precipitate of albumin which may be pro- 

 duced, 5 c.c. of the solution of copper 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. 2 The liquid is filtered and 

 to the nitrate, 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." 



Mercuric Oxide Reduction Test (Cramer). 3 This test depends on 

 the reduction of mercuric oxide in a weakly alkaline solution with the 

 formation of metallic mercury. The degree of alkalinity is an impor- 

 tant factor, as the test becomes more sensitive but less specific the 

 greater the alkalinity of the reagent. 



Apply the test as follows : 



Introduce 3 c.c. of Cramer's "2.5 standard reagent" 4 into a test-tube and heat 

 to boiling. The reagent remains clear but becomes slightly yellow. Add 3 c.c. 

 of urine and heat the mixture to boiling. Remove the tube from the flame, and 



1 Haines solution may be prepared by dissolving 8.314 grams of copper sulphate in 

 400 c.c. of water adding 40 c.c. of glycerol and 500 c.c. of 5 per cent potassium hydroxide 

 solution. 



2 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 

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

 solution, and heating the mixture to boiling. 



3 Cramer: Bioch. Jour., 9, 156, 1915. 



4 See Chapter II, page 28. 



