182 



PHYSIOLOGICAL CHEMISTRY 



salting-out process is entirely analogous to the salting-out of proteins (see page 

 102). 



9. Formation of Insoluble Soaps. Introduce 5 c.c. of soap solution into each 

 of two test-tubes. To the contents of one tube add a small amount of a solution 

 of calcium chloride and to the contents of the other tube add a small amount 

 of a solution of magnesium sulphate. Note the formation of insoluble soaps of 

 calcium and magnesium. 



10. Palmitic Acid. (a) Examine the crystals under the microscope and com- 

 pare them with those shown in Fig. 53, below. 



(b) Solubility. Try the solubility of palmitic acid in the same solvents as used 

 on fats (see page 180). 



(c) Melting-point. Determine the melting-point of palmitic acid by one of 

 the methods given on page 183. 



FIG. 53. PALMITIC ACID. 



(d) Formation of Transparent Spot on Paper. Melt a little of the fatty acid 

 and allow a drop to fall upon a piece of ordinary writing paper. How does this 

 compare with the action of a fat under similar circumstances? 



(e) Acrolein Test. Apply the test as given under 4, page 180. Explain the 

 result. 



(f) Iodine Absorption Test. For directions see Experiment 13. 



n. Saponification of Lard. To 25 grams of lard in a flask add 75 c.c. of 

 alcoholic-potash solution and warm upon a water-bath until saponification is 

 complete. (This point is indicated by the complete solubility of a drop of the 

 solution when allowed to fall into a little water.) Now transfer the solution from 

 the flask to an evaporating dish containing about 100 c.c. of water and heat on a 

 water-bath until all the alcohol has been driven off. Precipitate the fatty acid 

 with hydrochloric acid and cool the solution. Remove the fatty acid which rises 

 to the surface, 1 neutralize the solution with sodium carbonate and evaporate to 

 dryness. Extract the residue with alcohol, remove the alcohol by evaporation 

 upon a water-bath and on the residue of glycerol thus obtained make the tests 

 as given below. 



12. Glycerol. (a) Taste. What is the taste of glycerol? 

 1 After drying the acid make an iodine absorption test as described in Experiment 13. 



