THE ALUMNI JOURNAL, 



187 



bore, with capillary ends. The follow- 

 ing data are necessary, viz : 



1 Weight of empty tube. 



2 " tube filled with water at 



15.5° c. 



3 Weight of tube filled with oil at 



155° c. 



It is evident that 2 — i-— weight of 

 the water, and 3 — i=weight ot the 

 ■equal volume of oil, then 



^--Sp. Gr. at 15.5° C. 



If a determination at 90° C. is to be 

 made, the Sprengel tube filled with oil 

 is suspended in boiling water for some 

 minutes until the desired temperature is 

 reached, then the excess of oil running 

 from the capillary ends is removed with 

 absorbent paper, the tube is removed from 

 the water, dried, cooled and weighed ; 

 this result may be called 4, then 

 £J--Sp. Gr. at99°C. 



Congealing point of an oil is usually 

 determined by placing a four ounce vial, 

 half filled with oil and carrying a ther- 

 mometer with bulb immersed in the oil, 

 in a freezing mixture of salt and ice in 

 an upright position. When the contents 

 are solid, remove the bottle from the 

 freezing mixture and place in a horizon- 

 tal position. Note the exact tempera- 

 ture at which the upright wall of frozen 

 fat melts down to a liquid. This is the 

 congealing point. 



Melting point is determined by filling 

 the bottom of a small cone of glass about 

 one inch long, with capillary point, made 

 from one-quarter inch bore tubing with 

 the fat. Strap one of these cones to the 

 bulb of the thermometer with a rubber 

 band, taking care to have the large end 

 of the cone up. Now immerse the ther- 

 mometer and cone in a beaker of dis- 

 tilled water, and raise the temperature 

 slowly to boiling, at a rate not exceeding 

 ■two degrees per minute. When the melt- 

 ing point is reached the particle of fat 



will instantly detach itself and rise to 

 the surface of the water at this moment 

 the reading of the thermometer must be 

 taken. Instead of pure water in the 

 bath it is frequently necessary to use a 

 solution of salt and water, say ten per 

 cent. This may be used in case the fat 

 is slightly water soluble, viz., butter, 

 cocoanut, stearine, etc. 



All of the above tests may be made on 

 the original glyceride or on the fatty 

 acids obtained Irom them by the process 

 of saponification and decomposition. 

 CHEMICAL TESTS. 



The most important of these are the 

 following: 



1. Saponification or Koetlstorfer pro- 

 cess. 



2. Reichert-Waller process. 



3. Iodine or Hiibel process. 



4. Acetyl process. 



The first applies to all saponifiable oils 

 and waxes, and distinguishes them from 

 each other and from the hydrocarbon 

 class. 



The second determines the amount of 

 volatile soluble fatty acids present, and 

 is important in butter analysis. 



The third applies to oils which are 

 unsaturated and absorb the halogen as 

 an additive compound, i. e., Oleins and 

 Linoleins, and also to hydrocarbons 

 which combine with the halogen by ad- 

 dition and by substitution, and in the 

 latter case yield hydriodic acid as a 

 bye-product. 



The third test serves to distinguish 

 the hydroxy fatty acids and their glycer- 

 ides, /. e., castor oil group, since they 

 alone have the property of taking on the 

 acetyl radicle. 



Besides these, are the sulphuric acid 

 color tests, useful when properly applied, 

 the silver nitrate reduction or Bechi 

 test, the elaidin test, the Maumene or 

 rise of temperature with concentrated 

 sulphuric acid, vide drying oils and Va- 



