CARBOHYDRATES AND RELATED BODIES. 2/ 



monocarboxylic acids, such as mannonic acid or dextronic 

 acid, and by the more pronounced oxidation they are converted 

 into dicarboxylic acids, as saccharic or mucic acid. 



A reaction of great importance in connection with the 

 hexoses is that which they exhibit when acted upon by phenyl 

 hydrazine. While this is a general aldehyde or ketone reac- 

 tion, the behavior of the hexoses is so characteristic as to 

 require mention. With one molecule of phenyl hydrazine, 

 C 6 H 5 NH NH 2 , the hexoses yield hydrasones, C 6 H 12 O 5 

 - X NH.C 6 H 5 , the ketone or aldehyde oxygen being 

 replaced by the hydrazine group. The hydrazones are mostly 

 soluble in water. An excess of phenyl hydrazine, enough to 

 give two molecules of that substance to one of the hexose, 

 yields bodies called osazones, which are mostly yellow, insol- 

 uble crystalline compounds of great importance for the sepa- 

 ration and identification of several of the sugars. They are 

 represented by the formula C 6 H 10 O 4 (N NH.C 6 H 5 ) 2 , and 

 by warming with strong hydrochloric acid they yield peculiar 

 compounds called osones, which are mixed ketone and alde- 

 hyde structures. These reactions will all be illustrated below. 



GLUCOSE (d-glucose), known also as dextrose, grape sugar, 

 or diabetic sugar, is the best known representative of the 

 group. It is found in honey and many fruit juices, often 

 associated with levulose or fruit sugar. It may be produced 

 by the action of weak acids on cellulose or starch and on the 

 large scale is so made from the latter substance. Weak sul- 

 phuric acid is commonly employed and the hydration or con- 

 version is effected under pressure. Hydrochloric acid is 

 sometimes employed in making a commercial glucose, while 

 with other acids the action is much slower or less complete. 

 In the section below on the behavior of starch the nature of 

 the reaction will be explained. The following experiment 

 will illustrate the production of the sugar by the aid of sul- 

 phuric acid : 



Ex. Make a paste by boiling about a gram of starch with 100 cc. of 

 water in a glass flask. Add 10 drops of dilute sulphuric acid (1:5) and 



