48 PHYSIOLOGICAL CHEMISTRY 



of sugar or glycogen from cellulose. 1 It is probable that the cellulose 

 which disappears from the intestine is transformed for the most part into 

 fatty acids. 2 



EXPERIMENTS ON CELLULOSE 



1 . Solubility. Test the solubility of cellulose in water, dilute and concentrated 

 acid and alkali. 



2. Iodine Test. Add a drop of dilute iodine solution to a few shreds of cotton 

 on a test-tablet. Cellulose differs from starch and dextrin in giving no color 

 with iodine. 



3. Formation of Amyloid. 3 Add 10 c.c. of dilute and 5 c.c. of concentrated 

 H 2 SO4 to some absorbent cotton in a test-tube. When entirely dissolved (with- 

 out heating) pour one-half of the solution into another test-tube, cool it and dilute 

 with water. Amyloid forms as a gummy precipitate and gives a brown or blue 

 coloration with iodine. 



After allowing the second portion of the acid solution of cotton to stand about 

 10 minutes, dilute it with water hi a small beaker and boil for 15-30 minutes. 

 Now cool, neutralize with solid KOH and test with Fehling's solution. Glucose 

 has been formed from the cellulose by the action of the acid. 



4. Ammoniacal Cupric Hydroxide Solubility Test (Schweitzer). Place a 

 little absorbent cotton hi a test-tube, add Schweitzer's reagent, 4 and stir the 

 cellulose with a glass rod. When completely dissolved acidify the solution with 

 acetic acid. An amorphous precipitate of cellulose is produced. 



5. Hydrochloric Acid Zinc Chloride Solubility Test (Cross and Bevan)'. 5 

 Place a little absorbent cotton in a test-tube, add Cross and Sevan's reagent, 6 

 and stir the cellulose with a glass rod. When solution is complete reprecipitate 

 the cellulose with 95 per cent alcohol. 



6. Iodine-Zinc Chloride Reaction. Place a little absorbent cotton or quantita- 

 tive filter paper in a test-tube and treat it with the iodine-zinc chloride reagent. 7 

 A blue color forms on standing. Amyloid has been formed from the cellulose 

 through the action of the ZnCU and the iodine solution has stained the amyloid 

 blue. 



7. Other Cellulose Solvents. It has been demonstrated by Deming 8 that 

 there are many excellent solvents for cellulose (filter paper). For example, 

 the concentrated aqueous solutions of certain salts such as antimony trichloride, 



1 Lusk: American Journal of Physiology, 27, 467, 1911; also Hoffmann, Inaugural dis- 

 sertation, Halle- Wittenberg, 1910. 



2 Tappeiner: Zeitschrift fur Biologic, 24, 105 1888. 



3 This body derives its name from amylum (starch) and is not to be confounded with 

 amyloid, the glycoprotein. 



4 Schweitzer's reagent is made by adding potassium hydroxide to a 5 per cent solution 

 of copper sulphate, which contains 5 per cent of ammonium chloride, until precipitation is 

 complete. A precipitate of cupric hydroxide forms and this is filtered off, washed, and 

 3 grams of the moist cupric hydroxide brought into solution in a liter of 20 per cent am- 

 monium hydroxide. 



6 Cross and Bevan: Chemical News, 63, p. 66. 



6 Cross and Bevan's reagent may be prepared by combining two parts of concentrated 

 hydrochloric acid and one part of zinc chloride, by weight. 



7 The iodine-zinc chloride reagent as suggested by Nowopokrowsky (Beihefte Botan. 

 Centr., 28, 90, 1912) may be made by dissolving 20 grams ZnCl 2 in 8.5 c.c. water and when 

 cool introducing the iodine solution (3 grams KI+i.5 gram I in 60 c.c. water) drop by drop 

 until iodine begins to precipitate. 



8 Deming: Journal American Chemical Society, 33, 1515, 1911. 



