EDIBLE OILS AND FATS. 31 



ing water and ice, until cold. The disk of fat is then dropped into the tube from the 

 spatula, and at once sinks until it reaches a part of the tube where the density of 

 the alcohol water is exactly equivalent to its own. Here it remains at rest and free 

 from the action of any force save that inherent in its own molecules. 



The delicate thermometer is placed in the test tube and lowered until the bulb is 

 just above the disk. In order to secure an even temperature in all parts of the 

 alcohol mixture in the vicinity of the disk, the thermometer is moved from time to 

 time in a circularly pendulous manner. 



The disk having been placed in position, the water in the beaker is slowly heated 

 and kept constantly stirred by means of the blowing apparatus already described. 



When the temperature of the alcohol-water mixture rises to about 6 C. below the 

 melting point, the disk of fat begins to shrivel and gradually rolls up into an irreg- 

 ular mass. 



The thermometer is now lowered until the fat particle is even with the center of 

 the bulb. The bulb of the thermometer should be small, so as to indicate only 

 the temperature of the mixture near the fat. A gentle rotary movement should be 

 given to the thermometer bulb. The rise of temperature should be so regulated that 

 the last 2 C. of the increment require about ten minutes. The mass of fat gradually 

 approaches the form of a sphere, and, when it is sensibly so, the reading of the ther- 

 mometer is to be made. As soon as the temperature is taken the tube is removed 

 from the bath and placed again in the cooler. A second tube, containing alcohol 

 and water, is at once placed in the bath. The test tube (ice water having been 

 used as a cooler) is of low enough temperature to cool the bath sufficiently. After 

 the first determination, which should be only a trial, the temperature of the bath 

 should be so regulated as to reach a maximum of about 1.5 above the melting point 

 of the fat under examination. 



The edge of the disk should not be allowed to touch the sides of the tube. This 

 accident rarely happens, but in case it should take place and the disk adhere to the 

 sides of the tube a new trial should be made. 



Triplicate determinations should be made, and the second and third results should 

 show a near agreement. 



Example: Melting point of sample of butter: Degrees. 



First trial ......................................................... 33. 15 C. 



Second trial ....................................................... 33. 05 C. 



Third trial ........................................................ 33.100. 



13. DETERMINATION OF MELTING POINT OF FATTY ACIDS. a 



Draw up the melted fatty acid into a very thin-walled capillary tube 1 or 2 inches 

 long according to the length of bulb of the thermometer used. Seal one end of the 

 tube and allow the fatty acid to cool on ice for from twelve to fifteen hours. Then 

 attach to the bulb of a delicate thermometer graduated to one-fifth degree, immerse 

 in a beaker of water, and warm up very slowly. The point where the acid becomes 

 transparent is taken as the melting point. 



14. DETERMINATION OF MAIMKM': NIMBKR." 



The following apparatus has been largely used by the writer and has given very 

 satisfactory results: 



A beaker, 5 inches by 1 inches, is placed inside ot another 6 inches by 3 inches, 

 and a wet mixture of asbestos and plaster of paris tightly packed around the inner 

 l>eaker. This, when dried, makes a hard, solid packing which radiates heat very 

 slowly. 



r. S. I>-pt. of AKF.. Div. of Clicin., Bui. i:?. pi. I. p. I Lv Bi-m-ilikt nn<l Lewkowitsch, Oils. KM!-. 

 find Wiixrs, p. -.17. Wik'v, I'rin. :iinl 1'nn-. A.rr. Anal., vol. 3. p. 321. 

 b AlK-ii. Coin. on,'. Annl., :><! rd., vol. '2, pt. 1. p. 7ti. 



