526 



EXCRETION 



melts at 205 C. To perform the test for dextrose in the 

 urine, proceed thus: Put 5 c.c. of urine in a test-tube, add I decigramme 

 of hydrochlorate of phenyl-hydrazine and 2 decigrammes of sodium 

 acetate. It is sufficiently accurate to add as much phenyl-hydrazine 

 as will lie on a sixpence (or a dime) and twice as much sodium acetate. 

 Heat the test-tube in a boiling water-bath for half an hour. Then cool 

 at the tap and examine the deposit under the microscope for the yellow 

 phenyl-glucosazone crystals (Fig. 196). Sometimes the osazone pre- 

 cipitate is amorphous. If this should be the case, the precipitate, if no 

 crystals can be seen, must be dissolved in hot alcohol. The solution is 

 then diluted with water and the alcohol boiled off, when the osazone, 



if any be present, will crystallize out. 

 Very minute traces of sugar can be 

 detected in this way (as little as oa per 

 cent, in urine). Often in normal urine 

 yellow crystals are deposited during 

 the first fifteen minutes' heating. 

 They must not be mistaken for gluco- 

 sazone. They probably consist of a 

 compound of glycuronic acid and 

 phenyl-hydrazine. They are changed 

 as the heating goes on into an amor- 

 phous brownish - yellow precipitate 

 (Abel). 



(d) The Yeast Test is an importanl 

 confirmatory test for distinguishing 

 the fermentable sugars from other re- 

 ducing substances, but it is not very 

 delicate, and will with difficulty detect 

 sugar when less than 0-5 per cent, is 

 present. It can be performed thus: 

 A little yeast (the tablets of com- 

 pressed yeast do very well) is added 

 to a test-tube half filled with urine. 

 The test-tube is then filled up with 

 mercury, closed with the thumb, and 

 inverted over a dish containing mer- 

 cury. The dish may be placed on the 

 top of a water-bath whose temperature 

 is about 40 C. After twenty-four 

 hours the sugar will have been broken 



up into alcohol and carbon dioxide. The latter will have collected 

 above the mercury in the test-tube, and the former will be present in 

 the urine. The tests for sugar will either be negative or will be less 

 distinct than before. A control test-tube containing water and yeast 

 should also be set up, as impurities in the yeast sometimes yield a small 

 amount of carbon dioxide. Specially- constructed tubes are also often 

 used for performing the test. 



(2) Quantitative Estimation of Sugar in Urine. (a) Volumetrically, 

 the sugar can be estimated by titration with Fehling's solution. As 

 this does not keep well, two solutions containing its ingredients should 

 be kept separately and mixed when required. Solution I.: Dissolve 

 34-64 grammes pure cupric sulphate in distilled water, and make up the 

 volume to 500 c.c. Solution II.: Dissolve 173 grammes Rochelle salt 

 in 400 c.c. of water, add to this 51-6 grammes sodium hydroxide, and 

 make up the volume with water to 500 c.c. Keep in well-stoppered 



Fig. 196. Phenyl-Glucosazone and 

 Phenyl-Maltosazone Crystals (Mac- 

 leod). The phenyl - glucosazone 

 crystals are in the upper part of 

 the figure, the phenyl-maltosazone 

 in the lower. 



