196 PROTEINS AND CARBOHYDRATES 
carded. If the solutions are satisfactory, the sugar solution should be 
added very slowly to the hot Fehling’s solution with boiling after each 
addition. The presence of reducing sugars will be indicated by a yellow- 
brown precipitate. 
Benedict’s Method for Reducing Sugars. This is a modification of 
Fehling’s test for reducing sugars. Instead of using the strong NaOH, 
Benedict has substituted NazCO3. Sodium citrate is used to keep the 
Cu(OH)2 in solution. The method for conducting the test is much like 
that for Fehling’s test. The solution should be boiled before using and 
allowed to cool. If reducing sugar is present the solution will turn first 
a green and later a yellow color. Benedict’s test is more delicate than 
the original Fehling’s method. The solutions are prepared as follows: 
Solution I. 
Copper sulphate.............. 34.65 gms. 
Distilled water..............-. 500.00 e.c. 
Solution ITI. 
Anhydrous sodium carbonate.... 100.00 gms. 
Rochelle salt..............-... 173.00 gms. 
Distilled water................ 500.00 c.c. 
Nylander’s Test for Reducing Sugars. Heat a few cubic centimeters 
of the solution under examination with $ c.c. of Nylander’s reagent. A 
black color is formed if a reducing sugar is formed which is due to a 
precipitation of the bismuth in the reagent. 
Phenyl-Hydrazine Reaction. With phenyl hydrazine osazones are 
formed by action with certain sugars. These are yellow crystalline 
substances which are characterized by a definite form typical for each 
different sugar. The test is carried out as follows: Put about 5 c.c. of 
the sugar solution into a small veaker or test tube and add about 1.5 c.c. 
of phenyl-hydrazine acetate solution. Heat on a water bath for three- 
quarters of an hour. Cool and examine the crystals under the micro- 
scope. 
Quantitative Determination of Dextrose. (Allihn’s Method.) 
Reagents. 
(a) Copper sulphate solution: 
Copper sulphate CuSO4-5H20...... 34.639 gms. 
Distilled water. ..............000. 500.000 c.c. 
(b) Alkalin tartrate solution: 
Rochelle salts. .............0..00. 173 gms. 
Potassium hydroxide.............. 125 gms. 
Distilled water. ..............0008 500 c.c. 
