XXXIV. The carbohydrates. 



1. Materials. Potato starch; dextrin; dextrose; maltose; 

 lactose; saccharose; cellulose represented by absorbent 

 cotton and ashless filter paper. 



2. Preparation. 



(1) To prepare Fehling's solution: 



a. Into a half-liter, glass-stoppered bottle put 34.64 

 gm. CuSO 4 c.p., and enough H 2 O dist. to make 

 500 c. c. Label the solution: Fehling's solution (a). 



b. Into a similar receptacle put 173 gms. of potassic- 

 sodic tartrate KNaC 4 H 4 O 6 -f 4H 2 O [Rochelle 

 salt] and 50 gm. of NaOH, weighed in sticks; add 

 enough water to make 500 c c. Label: Fehling's 

 solution (). For use mix these two solutions in 

 equal parts. A convenient quantity for the follow- 

 ing experiments is 50 c. c. of each in 100 c. c. bottle. 



(2) Prepare a starch paste by rubbing 1 gm. of starch to a 

 creamy consistence with water, add 100 c. c. of distilled 

 water and boil, 



(3) Prepare a dilute solution of iodine by direct solu- 

 tion in water or by diluting an alcoholic solution. 



j. Experiments and Observations. 



(1) Put a little dry starch into an evaporating dish; add 

 some dilute iodine. The starch turns blue. Pour a 

 few drops of starch paste into a test tube; add a few 

 drops of iodine. Iodine may be used to detect the 

 presence of raw or of cooked starch. 



(2) Put some raw starch into a test tube or beaker; add 

 water; stir. The starch does not seem to be at all 



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