PHYSIOLOGICAL CHEMISTRY. 



Fio. 39. 



formed in which the soap is insoluble. This salting-out process 

 is entirely analogous to the salting-out of proteins (see page 99). 

 9. Palmitic Acid. (a) Examine the crystals under the micro- 

 scope and compare them with those shown in Fig. 38, p. 137. 



(b) Solubility. Try the solubility 

 of palmitic acid in the same solvents as 

 used on fats (see page 135). 



(c) Melting-Point. Determine the 

 melting-point of palmitic acid by one of 

 the methods given on page 139. 



(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 135. Explain 

 the result. 



10. Saponifi cation 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 saponi- 

 fication 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 trans- 

 fer 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, neu- 

 tralize 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. 



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



(b) Solubility. Try the solubility of glycerol in water, alcohol 

 and ether. 



(c) Acrolein Test. Repeat the test as given under 4, page 135. 



MELTING-POINT APPARATUS. 



