158 COMPOSITION OF THE BODY 



3. Add a little Fehling's solution to the starch solution and 

 boil. No reduction. 



4. Boil some of the solution with a little dilute hydrochloric 

 acid for half an hour. As soon as the solution begins to clear 

 soluble starch is formed. Draw off a little of this and test with 

 iodine solution. Amylodextrin (soluble starch) gives a blue color. 

 A little later try the same reaction. A red color indicates eryth- 

 rodextrin. When no coloration follows the addition of iodine the 

 starch may all be considered inverted although some achroodex- 

 trin may still be present. Boil some of the solution, neutralized 

 with sodium carbonate, with Fehling's solution. A reduction of 

 the solution follows. 



5. Add to 20 cc. of the solution 10 cc. of malt diastase solu- 

 tion (See page 151) and try the same reactions as in 4. 



225. Cellulose. Cellulose, like starch, is insoluble in water and 

 all the weaker solvents. Some reagents dissolve it, and from 

 these solutions it may be precipitated practically unchanged. It 

 occurs in all the tissues of the higher plants. 



1. It is soluble in ammoniacal solution of cupric oxide and is 

 precipitated from this solution by acids. Try dilute hydrochloric. 



2. Cellulose gives a blue color with sulphuric acid and iodine, 

 but no color with iodine alone. 



3. Dissolve some cellulose in a concentrated acid. Add water 

 and note the gelatinous precipitate, which is called amyloid and 

 gives a blue color with iodine. 



4. DETERMINATION OF CELLULOSE. Extract a few grams of 

 tissue with ether. After removing the ether thoroughly from the 

 residue by drying at a temperature below 40 C, place the re- 

 sidual substance in a hard glass beaker with 200 cc. of boiling 

 1.25 per-cent. sulphuric acid. Cover the beaker with a watch 

 glass and continue boiling for thirty minutes. Wash the tissue 

 on a filter with hot water until all the acid is removed. Return 

 the material to the same beaker and add 200 cc. of boiling sodium 

 hydrate. Continue the boiling for thirty minutes, wash the tissue 

 free of alkali, dry, weigh and incinerate. The loss of weight after 



