CARBOHYDRATES. 25 



the phenylhydrazine-acetate solution furnished by the instructor, 1 

 and heat on a boiling water-bath for one-half to three-quarters of 

 an hour. Allow the liquid to cool slowly and examine the crystals 

 microscopically (Plate III, opposite p. 24). 



The phenylhydrazine test has been so modified by Cipollina as 

 to be of use as a rapid clinical test. The directions for this test 

 are given in the next experiment. 



4. Cipollina's Test. Thoroughly mix 4 c.c. of dextrose solu- 

 tion, 5 drops of phenylhydrazine (the base) and ^ c.c. of glacial 

 acetic acid in a test-tube. Heat the mixture for about one minute 

 over a low flame, shaking the tube continually to prevent loss of 

 fluid by bumping. Add 4-5 drops of sodium hydroxide (sp. gr. 

 1. 1 6), being certain that the fluid in the test-tube remains acid, 

 heat the mixture again for a moment and then cool the contents 

 of the tube. Ordinarily the crystals form at once, especially if the 

 sugar solution possesses a low specific gravity. If they do not 

 appear immediately allow the tube to stand at least 20 minutes 

 before deciding upon the absence of sugar. 



Examine the crystals under the microscope and compare them 

 with those shown in Plate III, opposite page 24. 



5. Precipitation by Alcohol. To 10 c.c. of 95 per cent alcohol 

 add about 2 c.c. of dextrose solution. Compare the result with 

 that obtained under Dextrin, 7, page 49. 



FIG. i. 



DIALYZING APPARATUS FOR STUDENTS' USE. 



6. Iodine Test. Make the regular iodine test as given under 

 >tarch, 5, page 44, and keep this result in mind for comparison 

 nth the results obtained later with starch and with dextrin. 



7. Diffusibility of Dextrose. Test the diffusibility of dextrose 



1 This solution is prepared by mixing one part by volume, in each case, of 

 glacial acetic acid, one part of water and two parts of phenylhydrazine (the 

 base). 



