214 III. CHEMISTRY OF NEUTRAL FATS 



(luantitics of fat, it is achisable to cany out the oxidation.s on a series of small 

 batches, using a maximum of 150 g. of fat for each run. 



Steger and Van Loon-^* have suggested an alternative procedure for 

 purification of the crude saturated triglycerides. This involves the extrac- 

 tion with light petroleiun ether (b.p. 40-60°C.) and removal of the acidic 

 products from this extract by shaking with ammonia in 50% aqueous alco- 

 hol. Some ammonium salts of the acidic products remain in the petroleum 

 ether. These can be partially removed by extraction with calcium chloride 

 solution, followed by water. After drying of the petroleum ether, the solvent 

 is removed by distillation. The residue is extracted with ethyl acetate, 

 which dissolves the saturated triglycerides and leaves behind any im- 

 purities such as the calcium salts of the acidic products. The pure satu- 

 rated triglycerides can be obtained by evaporation of the ethyl acetate. 



(6) Estimation of Partially or Completely Unsaturated Triglycerides 

 (Hilditch) . If the total fatty acid content of the fat is known, the limiting 

 amount of fractions II and III (GS2U and GSU2) can be calculated by sub- 

 tracting the saturated acid content (e.xpressed in molar per cent) in the 

 saturated triglyceride portion from the total saturated fatty acid content. 

 The amount of any two groups of the unsaturated fractions (GS2U, GSU2, 

 and GU3) can readily be estimated if any one of the three groups is absent 

 or its amount is known. 



If such data are not available, one may readily calculate the limiting 

 values of GU3. The minimum quantity of triunsaturated glyceride can be 

 estimated by assuming that the saturated acids present in the mixed tri- 

 glyceride are associated with the maximum quantity of unsaturated acids, 

 i.e., as GSU2. The smallest possible amount of GU3 will obviously be de- 

 termined by the difference between the total unsaturated acids and the un- 

 saturated acids present in the mixed triglyceride. 



On the other hand, the greatest possible amount of GU3 which may be 

 present can be calculated by assuming that the excess saturated acids are 

 associated with a minimum of unsaturated acids in the mixed triglycerides, 

 i.e., as the GS2U. Hilditch''^ states that, in most cases, the proportion of 

 GU3 tends to approximate the minimum rather than the maximum possible 

 percentage. 



Some idea of the total GU3 content can be arrived at by the estimation of 

 the tristearin content of completely hydrogenated fat, as well as l)y a study 

 of the glyceride composition of the fat after partial hydrogena- 

 tion.^^^'^^"'^^^"^^^ This procedure is of value because of the fact that the 



^^ A. Steger and J. Van Loon, Rec. trav. chim., 54, 284-288 (1935). 

 259 T. P. Hilditch and E. C. Jones, /. Chem. Soc, 1932, 805-820. 

 2«> A. Banks, H. K. Dean, and T. P. Hilditch, J. Soc. Chem. Ind., 54, 77-82T (1945). 

 2" N. R. Dhingra, T. P. Hilditch, and A. J. Rhead, /. Soc. Chem. Ind., 51, 195-198T 

 (1932). 



262 T. P. Hilditch and W. J. Stainsby, Biochem. J., 29, 90-99 (1935). 



2«3 T. P. Hilditch and H. M. Thompson, J. Soc. Chem, Ind., 56, 434-438T (1937). 



