ISO AGRICULTURAL CHEMISTRY 



fiber and cellulose are not identical terms. In the chem- 

 ical analysis of plants, the crude fiber is determined by 

 first digesting the material in dilute sulfuric acid to 

 dissolve all soluble bodies as sugar, hydrolyzed starch, 

 some of the proteids and related bodies. The substance 

 is then digested with dilute sodium hydroxid to remove 

 all compounds which have failed to dissolve in the acid. 

 Crude fiber and insoluble mineral matter are about the 

 only substances which are insoluble in the dilute acid and 

 alkali, hence the fiber is obtained by dissolving all other 

 compounds and deducting the insoluble mineral matter 

 left. For the determination of cellulose more exact 

 methods have been devised. The crude fiber determina- 

 tion, however, is valuable because it shows the amount 

 of fibrous material contained in plants. 



Experiment 45. Preparation of cellulose. Place in a beaker 

 about i gram of ground straw or hay ; add 200 cc. of water, and 

 20 drops of H 2 SO 4 . Boil on the sand-bath twenty minutes, and 

 after the material settles, pour off the liquid, then add 100 cc. water, 

 and wash thoroughly by decantation. Add 200 cc. water and 4 cc. 

 NaOH solution, boil twenty minutes, and wash the fibrous material 

 as before. Place some of the crude fiber in a test-tube, add 5 cc. 

 HC1, 10 cc. H 2 O, and a crystal of KC1O 3 ; heat, and then wash the 

 cellulose product. 



Questions, (i) What element was liberated by the action of 

 HC1 upon theKC!O 3 ? (2) What effect did this element have in the 

 bleaching and purification of the crude fiber? (3) In what other 

 experiment has this element been used as a bleaching reagent? 



(4) When examined with a lens, how did the cellulose appear ? 



(5) Is cellulose soluble in dilute acids? (6) Why were the dilute 

 acid and alkali solutions used in this experiment? (7) What be- 

 comes of the ash or mineral matter in the material used in this ex- 



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