110 FATS 



table fats, unless meat and dairy products were at the same time very 

 deficient in the dietary. 



The unsaturated bonds in the oleates also confer upon them the 

 property of absorbing halogens, and the power of various natural 

 fats and oils to absorb iodine is used as a means of characterizing and 

 identifying them. The "Iodine Number" is the number of grammes of 

 iodine which is absorbed by a hundred grammes of fat dissolved in 

 chloroform and treated with a solution of iodine in alcohol or acetic 

 acid. Other characteristics which are employed to differentiate the 

 natural fats are: The "Hehner Number" or weight of water-insoluble 

 fatty acids yielded by 100 grammes of fat; the "Acid Number" or 

 proportion of free fatty acid in the fat, estimated by titration in 

 alcoholic solution; the "Reichert-Meissl Number," or proportion of 

 volatile fatty acids yielded by distilling the hydrolyzed fats with 

 steam; the Saponification-value or milligrammes of potassium hydroxide 

 neutralized by the saponification of one gramme of the fat; and 

 the Acetyl Number, or amount of acetic acid yielded by 1 gramme of 

 fat after treatment with hot acetic anhydride. In the following table 

 the melting-points, iodine numbers and saponification-values of some 

 of the fats most commonly employed are enumerated: 



Saponification 

 Fat. Melting-point. Iodine number. value. 



Butter-fat 28-33 C. 26- 38 220-233 



Pork-fat 36-46 C. 50- 70 195-197 



Beef-fat . . . . . 40-48 C. 36-48 193-200 



Sheep-tallow 44-49 C. 33- 46 192-195 



Human fat 

 Cod-liver oil 

 Cotton-seed oil 

 Olive oil . . 

 Linseed-oil 



17.5 C. 57- 66 193-199 



0-10 C. 144-168 175-193 



3- 4 C. 105-117 191-196 



2-10 C. 78- 91 185-194 



-27 C. 173-202 190-195 



Cod-liver Oil is of especial interest to the physician because of its 

 widespread employment as a food and therapeutic agent in chronic wast- 

 ing diseases such as tuberculosis, and rickets. It is obtained from the 

 livers of codfish by extraction with steam and water. It consists of a 

 mixture of the glycerides of a great variety of saturated and unsatur- 

 ated fatty acids together with a considerable proportion of phos- 

 pholipins, a small amount of cholesterol, numerous nitrogenous bases 

 and traces of iron, manganese, bromine and iodine. The therapeutic 

 value of the oil has been variously attributed to each of these con- 

 stituents in turn, and on the other hand to the readily digestible char- 

 acter of the oil itself. Modern opinion inclines to the view that the 

 efficacy of cod-liver oil resides mainly in its high calorific value, and 

 the fact that it is usually added in considerable dosage to the pre- 

 established dietary. On the other hand it is very rich in accessory 

 foodstuffs and the possible significance of some of these must not 

 be overlooked. From this point of view it is not impossible that the 

 therapeutic applications of cod-liver oil may be destined to increase 

 rather than to diminish, as our growing knowledge of the exact require- 



