CH. V.] GLUCOSE. 109 



heat to boiling. Maintain active boiling for 50 sees., shaking from 

 side to side to prevent spurting. Immediately add 4 drops of a 

 mixture of equal parts of glycerol and 10 per cent, copper sulphate. 

 Shake for a moment to mix and allow to stand without further heat- 

 ing for i minute. The blue colour is discharged, and a yellowish 

 precipitate of cuprous hydroxide forms. 



Repeat the experiment, using 5 cc. of the solution diluted I in 

 10 and i in 100. (Cole's test.) 



NOTE. The test was elaborated by the author for the detection of very 

 small quantities of glucose in urine (see Ex. 381). It is very sensitive, and it is 

 claimed that i part of glucose in 500,000 parts of distilled water can be detected 

 by this means. The instructions given are to be strictly followed. Many 

 samples of glycerol give a slight reduction when boiled with sodium carbonate 

 and copper sulphate, but they do not give a reduction when treated in the way 

 described. The function of the glycerol is to keep the cupric carbonate in 

 solution. 



105. To 2 cc. of Nylander's reagent add 10 cc. of the glucose 

 solution, mix, and boil. Immerse the tube in a beaker of boiling 

 water for five minutes. A black precipitate of metallic bismuth 

 separates out. (Nylander's test.) 



NOTES. i. Nylander's reagent is prepared by dissolving 50 grams, of 

 Rochelle salt and 20 grams, of bismuth subnitrate in i litre of 8 per cent, 

 sodium hydroxide. 



2. The test is used for detecting small amounts of glucose in urine. It is 

 superior for this purpose to Fehling's solution since it is not readily reduced by 

 urates, creatinine, etc. The introduction of Benedict's solution and Cole's 

 test have, however, led to the disuse of Nylander's. 



106. Treat 2 cc. of a o-i per cent, solution of safranine with 

 2 cc. of the glucose solution and 2 cc. of 5 per cent, sodium hydroxide. 

 Mix and boil, avoiding any shaking. The opaque red colour gives 

 place to a light yellow, owing to the reduction of the safranine to a 

 " leuco-base." 



107. To 3 cc. of the 0-2 per cent, glucose add T cc. of a solution 

 of sulphindigotate of soda and a large " knife point " of anyhdrous 

 sodium carbonate and boil. The blue colour turns green, purplish, 

 red, and finally yellow. Shake with air : the blue colour reappears. 

 (Mulder's test.) 



NOTE. These two experiments illustrate the reducing properties of glu- 

 cose in hot alkaline solution. The avidity of the reduced leuco-bases for 

 oxygen is shown by the reappearance of the colour on cooling and shaking 

 with air. 



