CONTENTS jjj 



III. The Chemistry of Neutral Fats (continued) 



(4) Synthesis of Fats from Petroleum I75 



4. Composition of Natural Fats and Oils 179 



( 1 ) Component Fatty Acids in Natural Fats and Oils .... . . . . . . . . 179 



a. Analysis of Fats ^-q 



(a) Fractionation into Saturated and Unsaturated Acids. . . 179 



(b) Fractional Distillation of Fatty Acid Mi.xtures 180 



(c) Non-solvent Crystallization 182 



(d) Crystallization from Solvents Ig2 



(e) Chromatographic Separation Ig3 



(f ) Countercurrent Distribution 184 



b. Animal Fats ,0^ 



, . ^ . . 184 



(a; Composition of Fats from Aquatic Forms 185 



(b) Composition of Fats from Land Animals ]'_ 191 



(c) Composition of Milk Fats I94 



c. Vegetable Fats , q^ 



(a) Fats with a High Content of Linoleic Acid ' . 196 



(b) Fats Containing Elaeostearic, Petroselinic or Erucic Acid 196 



(c) Fats Containing a Large Proportion of Saturated Short- 



Chain Acids 201 



(d) Fats Containing Large Amounts of Stearic Acid 204 



(e ) Fats Containing Definite Amounts of the Saturated Coq-^ 



Acids " " 204 



(2) Glyceride Components of Natural Fats and Oils ' 207 



a. Specific Glycerides Isolated from Natural Fats and Oils . .. . 207 



(a) Simple Triglycerides Isolated from Natural Fats and Oils 207 



(b) Mixed Triglycerides Isolated from Natural Fats and Oils 209 



b. Methods of Analysis for the General Class of Triglycerides ... 210 



(a) Determination of Fully Saturated Glycerides (Hilditch) . 211 



(b) Estimation of Partially or Completely Unsaturated Tri- 



glycerides (Hilditch) 214 



(c) Estimation of Triglyceride Structure by Low-Tempera- 



ture Crystallization (Brown) 215 



c. Theories Advanced to Explain the Glyceride Composition of 



Natural Fats and Oils 216 



(a) Monoacid Theory 217 



(b) Theory of "Even" Distribution ' ^ ^ ^ ^ 217 



(c) Theory of Random Distribution 223 



(d) Theory of Partial Random Distribution 229 



d. Glyceride Composition of Fats 231 



5. Constants Used for Identification of Fats and Oils 234 



(1) Melting Point 237 



(2) Specific Gravity 2S» 



(3) Refractive Index 239 



(4) Saponification Number 240 



(5) Free Fatty Acids 241 



(6) Iodine Number 242 



(7) Thiocyanogen Number 244 



(8) Reichert-Meissl Number 245 



(9) Polenske Number 246 



(10) Acetyl Number 246 



