CH. V.] * FRUCTOSE. Ill 



drops should be dissolved in a few cc. of strong acetic acid, and added to the 

 sugar solution. 



3. Phenyl-hydrazine hydrochloride, C 6 H 5 .NH.NH 2 .HC1 does not give 

 an osazone when boiled with glucose, unless an excess of sodium acetate be 

 added. This acts on the hydrochloride to form phenyl-hydrazine acetate and 

 sodium chloride. In the author's experience it is advisable to have some free 

 acetic acid present. 



4. The osazone can be recrystallised as follows : Filter the cold solution 

 through a small paper. Wash well with cold water. Boil a little strong alcohol 

 in a tube and pour the hot solution on to the paper. Collect the filtrate in a 

 clean tube, boil it, and pass it back through the paper. Repeat the process 

 until a strong alcoholic solution is obtained. Heat it again, and gradually add 

 boiling water until a faint turbidity is produced. Heat again, add alcohol 

 until the solution is just clear again, and then allow the tube to cool slowly. 

 Or the alcoholic solution can be concentrated slightly on a boiling water bath. 

 The product obtained can be filtered, washed and dried in a steam oven. The 

 melting point is 204 to 205 C. 



no. To about 2 cc. of the solution add 6 drops of a I per cent, 

 alcoholic solution of a-naphthol. To this mixture add about 2 cc. 

 of strong sulphuric acid, running it down the side of the tube. A 

 purple ring is formed at the junction of the fluids. 



NOTE. This reaction is given by all carbohydrates (see Ex. 26). Furfurol 

 is formed very readily from fructose, sucrose and the pentoses. A modifica- 

 tion of the test that only succeeds with these sugars is given in Ex. 114. 



Fructose (laevulose or fruit-sugar) is a keto-hexose. 

 It can be prepared by the acid hydrolysis of inulin, a 

 porysaccharide found in the tuberous roots of the dahlia, 

 dandelion, Jerusalem artichoke and Inula Helenium, from 

 which plant the name inulin is derived. It can also be 

 prepared by hydrolysing cane sugar with dilute acid and 

 separating the fructose from the glucose by adding calcium 

 hydroxide to the cooled solution. Calcium fructosate 

 crystallises out, and can be decomposed by oxalic acid. 

 It is rather difficult to obtain crystals of the sugar. 



For the following reactions use a dilute solution of 

 commercial fructose. Certain of the reactions can be 

 demonstrated by the use of a i per cent, solution of "invert 

 sugar," obtained by boiling loocc. of i per cent, cane sugar 

 with i cc. of strong hydrochloric acid for two minutes. 



in. Repeat Exercises 95 to 97. They are all obtained. 



