ORGANS AND PROCESSES OF DIGESTION 



65 



in another tube. Do the salts dissolve? Soluble salts may 

 be digested in all parts of the digestive tube, since all con- 

 tain water. Salts which are insoluble require special treat- 

 ment. 



Place some phosphate of lime in the 10% hydrochloric 

 . acid. What happens? Is this solution? To determine this 

 point pour some of the lime and acid mixture into an evap- 

 orating dish and evaporate to dryness. Does the residue 

 taste like phosphate of lime? Is it soluble in water? Since 

 the hydrochloric acid is used up, the action is not that of 

 an enzyme. The resulting residue is not phosphate of lime; 

 hence the action is not a simple solution. What has taken 

 place is a chemical combination of hydrochloric acid and the 

 phosphate, producing a salt which is soluble in water. This 

 process illustrates a method of converting insoluble salts into 

 forms soluble in water, and is a process that takes place in 

 the stomach. 



XL. TABULATION OF NUTRIENT DIGESTION (OPTIONAL). 



Directions. Fill out the following table from the results 

 obtained in the preceding exercises. If a given nutrient 

 is digested by more than one reagent, indicate by separate 

 entries for each as indicated in the table. 



