CARBOHYDRATES 219 



v. Nylander's Reagent contains bismuth subnitrate, Kochelle 

 salt and potassium hydroxide. To about 3 c.c of undiluted dex- 

 trose solution add about %-l c.c of Nylander's reagent and boil 

 3-4 minutes. The liquid darkens as the result of the formation 

 of metallic bismuth. This test is sometimes called the Almen, or 

 Almen-Nylander test. 



vi. The Phenylhydrazine Test depends on the formation of 

 osazones, relatively insoluble compounds of phenylhydrazine and 

 sugars. 



In a test tube mix 5 drops phenylhydrazine, 10 drops glacial 

 acetic acid and 15 drops saturated sodium chloride. To the re- 

 sulting solid add about 3 c.c. of dextrose solution and boil for 

 2-3 minutes. Allow to stand. Examine crystals under the micro- 

 scope and draw. The osazones form yellow needles which often 

 group together in rosettes, sheaves, or fans. Many of the sugars 

 may be identified by the crystal form or the melting point of 

 their osazones. 



vii. Molisch's Test. To about 5 c.c. of dextrose solution add 2 

 drops of Molisch's reagent (15% alcoholic oc naphthol). In- 

 cline the test tube and pour concentrated sulphuric acid care- 

 fully down the side to form a layer at the bottom of the tube. 

 Notice the reddish violet ring at the junction of the two liquids. 

 This test is extremely delicate, but is given by various substances 

 other than carbohydrates. A negative result is good evidence 

 that carbohydrates are absent. A positive test, however, may 

 be due to other substances or to shreds of filter paper (cellulose). 



viii. Heat a small portion of dry dextrose in a test tube. Note 

 the brown color and the odor of caramel. If a small amount of 

 sugar is heated in a test tube with concentrated potassium 

 hydroxide, a similar result is observed, the color and odor 

 of caramel appearing. This is known as Moore's test. 



ix. Optical Activity. Carefully read the discussion of optical 

 activity in the text. The specific rotation of dextrose is +52.5 

 at 20 C. provided the concentration is not above 15%. With a 

 polariscope determine the rotary power of the dextrose solu- 



