198 AGRICULTURAL CHEMISTRY 



as in the manufacture of linseed, rape, cottonseed and 

 other oils. It is also extracted by means of solvents as 

 benzine and carbon disulfid. In roots and stems, fat is 

 found only in traces. In leaves, it is often present in the 

 form of a waxy coating, while in nuts it is frequently 

 stored up in large amounts in the kernel. 



261. Physical Properties. Fats are all characterized 

 physically by being insoluble and of a lower specific 

 gravity than water. There are a great many separate 

 fats, and each has its own specific gravity and melting- 

 point. As commonly found, they are not simple bodies, 

 but mechanical mixtures of various separate fats, as 

 stearin, palmitin, and olein. The fats are all soluble in 

 ether, chloroform and turpentine, and differ in physical 

 properties according to the proportion and kind of fats 

 present. When examined under the microscope, some 

 have optical properties and definite crystalline forms. 



262. Chemical Composition. Fats are all characterized 

 by having a high per cent, of carbon and a low per cent, 

 of oxygen. For example, in stearin C 57 H no O fr , there are 

 in the molecule 57 atoms of carbon, and 6 atoms of 

 oxygen. In starch and carbohydrates in general, the per 

 cent, of oxygen is greater, and of carbon, less than in 

 fats. 



ULTIMATE COMPOSITION OF FATS. 



Stearin. Palmitin. Olein. Starch. 



Per cent. Per cent. Per cent. Per cent. 



Carbon 77.6 75.9 77.4 44.44 



Hydrogen 12.4 12.2 n.8 6.17 



Oxygen 10.0 11.9 10.8 49-39 



