THE FATS. 29 



solution with dilute hydrochloric acid, filter out the palmitic acid, 

 wash it with cold alcohol until it is white, dissolve it in the least 

 possible quantity of hot alcohol and let it stand until it is cold. 

 Examine with a microscope the crystals which have separated and 

 make sketches of them. Test the reaction to blue litmus paper. 



62. THE PREPARATION OF PURE SOAP. Melt at a low tem- 

 perature most of the palmitic acid from the last experiment and 

 slowly add sodium hydrate solution until the reaction is alkaline, 

 warming meanwhile. A hard soap is produced. (Write the equa- 

 tion.) If a little alcohol is mixed with this before it cools a 

 transparent soap results. 



63. Hold a piece of small glass tubing in the Bunsen flame 

 until it is soft, turning it continually. Then draw it out into a 

 capillary tube about six inches long. Break this in the middle, 

 forming two open capillaries each with a large end. Melt a fat 

 at low temperature and draw it up into the capillary by exhaust- 

 ing the air, allowing it to cool and solidify there. Seal up the 

 large opening by means of a blast lamp or Bunsen burner. At- 

 tach the tube to the bulb of a thermometer by means of a rubber 

 band cut from a piece of tubing. Hold this in a beaker of water, 

 warming the latter slowly. Make a note of the melting point 

 the temperature at which the fat liquifies. In this manner deter- 

 mine the melting points of a number of fats, like mutton-tallow, 

 beef-tallow, lard, butter, also of palmitic acid and stearic acid, 

 beef tallow, lard, butter, also of palmitic acid and stearic acid. 

 Hand in the results. Place the thermometer with the capillary 

 of melted fat in water a little above its melting point and let it 

 cool slowly, noting the point at which solidification occurs. Notice 

 that this is below the melting temperature and that it varies with 

 the speed of cooling. 



64. Try the solubility of fate, fatty acids and soaps in 

 chloroform, ether, water, hot and cold alcohol. Tabulate the re- 

 sults and determine what methods can be employed for their 

 separation. 



65. Make the acrolein test upon the water-free glycerin by 

 heating in a dry tube with some crystals of potassium bisulphate. 

 The glycerin is decomposed, giving the acrolein odor, and showing 

 that the odor when obtained from fats is due to the glycerin radi- 

 cal, and not to the acid part. 



