ORGANIC COMPOUNDS OF PLANTS 203 



in straw it is less than i per cent. In nearly all food 

 products, the per cent, of pure fat is included with the 

 ether extract. 



Experiment 53. Fat from wheat germ. Place 2 grams wheat 

 germ in a test-tube, and add gasoline until the test-tube is about 

 one-third full. Cork and shake at intervals of three or four min- 

 utes. Do not let the gasoline come near the gas flame. Filter into 

 a clean porcelain dish, and place the dish in an open window until 

 the gasoline is evaporated. Observe the residue of fat. 



Experiment 54. Fat from yolk of egg. Repeat the preceding 

 experiment, using one-fourth of the yolk of a hard boiled egg, and 

 5 cc. ether instead of gasoline. 



Questions. ( i ) What was the solvent used for separating the 

 fat from the wheat germ? (2) From the yolk of the egg? (3) 

 Describe the fat obtained from the wheat germ. (4) From the 

 yolk of the egg. (5) How were the solvents removed in these 

 experiments? (6) Are fats volatile bodies ? (7) Why do fats ob- 

 tained from different sources vary in appearance and properties ? 



272, Ether Extract. The term ether extract is applied 

 to that class of compounds which is soluble in ether. In 

 the case of human foods, the ether extract consists largely 

 of fats and oils with variable amounts of waxes, resins, 

 chlorophyl, vegetable color ing- matters and nitrogenous 

 and phosphorized bodies as lecithin. The value of the 

 ether extract depends entirely upon its source ; in milk, 

 meats, and cereals and their products, the ether extract 

 is nearly pure fat, while in many vegetables it is less 

 than half fat. Methods of chemical analysis have not, 

 as yet, been sufficiently perfected to allow the separation 

 and determination of the pure fat of all materials. The 

 ether extract is obtained by placing a small weighed 

 amount of the dry material in a tube, 3, (Fig. 79) which 



