SALIVARY DIGESTION 261 



c. 1. Test saliva for chlorides and for sulphates. 



2. For sulphocyanates as follows: To 2 c.c. of saliva in a 

 small evaporating dish, add a few drops of dilute HC1 and 

 then a drop or two of dilute ferric chloride. A reddish color 

 indicates the presence of sulphocyanate. Compare the color 

 with that produced by adding a similar amount of ferric 

 chloride to distilled water and HC1 in an evaporating dish. 

 Note that the color is a pure greenish yellow with no sugges- 

 tion of pink. To this control add a few drops of dilute potas- 

 sium sulphocyanate. A comparison of this color with that 

 obtained with saliva will indicate the very small amount of 

 sulphocyanate in the latter fluid. 



3. Phosphates and carbonates also occur in the saliva and 

 may be detected by appropriate tests. 



d. Ptyalin. This ferment acts on starch, breaking it down 

 into dextrins, maltose, and isomaltose. It may be isolated by 

 precipitation with alcohol. Its action may be studied, how- 

 ever, without isolation. Saliva is said to contain an erepsin, 

 which acts on peptids. Its action is unimportant, however. 

 Saliva contains no lipase. 



II. Digestive Action. 



a. On Starch. Prepare a starch mucilage by mixing about 

 one gram of starch with 25 c.c. cold distilled water. Add about 

 75 c.c. of boiling water and boil for 15 minutes, stirring occa- 

 sionally and adding water to replace loss by distillation. Cool, 

 and use this mucilage in the following experiments. 



Arrange 6 test tubes as follows: 



1. 6 c.c. distilled water and a few grains of raw starch. 



2. 5 c.c. water, 1 c.c. saliva and a few grains of raw starch. 



3. 1 c.c saliva and 5 c.c starch mucilage. 



4. 1 c.c. saliva and 5 c.c. starch mucilage and 3 drops 10% 

 NaOH. 



5. 1 c.c saliva and 5 c.c starch mucilage and 5 drops 10% 

 HC1. 



