[o£nH| if present m 

 s to 06 obtained. 



28 



reaction^^l if present must be removed if a reliable sugar 

 test is 



71^ Tfie Phenyl-hydrazine Test. To 5 drops of phenyl- 

 hydrazine and 10 drops of glacial acetic acid in a test tube is 

 added 1 cc. of a saturated solution of sodium chloride. After 

 shaking- the mixture, add 3 cc. of the dextrose solution and 

 heat the test tube for about two minutes. The fluid is then 

 allowed to cool slowly in order that the crystals may form. 

 The canary yellow precipitate may be examined in from 20 to 

 60 minutes under the microscope for the characteristic glu- 

 cosazone crystals. 



The following test also -gives good results, but is longer : The Phenyl- 

 hydrazine Test. To about 10 cc. of the glucose solution in a test-tube add 0.2 

 gram of phenylhydrazine hydrochlorate, and 0.3 gram of sodium or pbtassium 

 acetate. Boil in the water-bath for 20-30 minutes ; then cool the test-tube by 

 allowing cold water to run upon it and set it aside. A yellow crystalline preci- 

 pitate is formed which is known as phenyl-glucosazone. Examine some of this 

 precipitate under a low power of the microscope and note the needle-like and 

 feathery crystals sometimes arranged in the form of rosettes. Phenyl-glucosa- 

 zone has a melting point of 204°C. 



72. Conversion of starch into glucose. Boil some of the 

 starch solution with a few drops of sulphuric acid until the 

 fluid becomes clear and a few drops of it give no blue color 

 with the iodine solution. Neutralize a small portion with 

 sodium carbonate ; test it for glucose. 



73. Crush a piece of condensed yeast about the size of a 

 pea. Place it in a test tube and add 10 cc. of the dextrose 

 solution. Agitate thoroughly and transfer the mixture to a 

 saccharometer. Leave in a warm place for 24 hours. If fer- 

 mentation occurs bubbles of carbon dioxide will be found in 

 the long arm of the saccharometer. 



74. Test a portion of the dextrose solution with Barfoed's 

 reagent. Compare with Fehling's. 



75. Lactose. Milk Sugar, (Ci,H,,Ojj-t-H,0). This is a 

 reducing sugar and is found in the milk of all mammals and 

 occasionally, during pregnancy, in the urine. Lactose is less 

 soluble in water than dextrose and is insoluble in alcohol. 

 With pure yeast it does not ferment. By the action of certain 

 other ferments, however it undergoes alcoholic fermentation, 

 with the production at the same time of lactic acid, forming 

 the drinks known as " koumiss " when made from mare's milk, 



