348 PRINCIPLES OF AGRICULTURAL CHEMISTRY 



sugar, while after drying at 100 C. only 2.04 per cent, was pres- 

 ent, a loss of nearly 50 per cent., due to decomposition. The de- 

 composition may produce volatile bodies, and thus give too high 

 results for water. 



Such materials should be dried in a vacuum, either at the 

 ordinary temperature, or at a slightly elevated temperature. The 

 drying may take place in a desiccator which contains sulphuric 

 acid and has been exhausted with a vacuum pump. 



(3) Volatile Materials. Some substances lose volatile organic 

 matter when dried at 100 in a current of air, or hydrogen. 



Silage loses acetic acid and ammonium acetate. Tobacco loses 

 moisture. Atwater found that meats and fish in drying lost I 

 to 4 per cent, of their total nitrogenous material. Animal excre- 

 ments, both liquid and solid, may lose nitrogen. 



These losses may in some instances be avoided by drying in a 

 vacuum. In others (as with urine and manure) analyses* should 

 be made on the fresh materials, and correction made for the loss. 



Ether Extract. The mixture of substances which is removed 

 from a plant by extraction with ether is termed ether extract. It 

 is often termed "fats and oils" and this expression is correct when 

 reference to concentrated feeding stuffs is intended, as in such 

 cases the ether extract is composed mostly of fats and oils. But 

 when applied to hays or fodders, the term "fats and oils" is not 

 correct, since the ether extract may contain 30 to 70 per cent, of 

 substances which are not fats or oils, such as chlorophyll, hydro- 

 carbons, and wax alcohols. 



Ether extract is obtained from all plants, and nearly all parts of 

 all plants. It is found in small quantities only, in roots and tubers, 

 in somewhat larger quantities in hays, and straws, and in com- 

 paratively large quantities in certain seeds, such as the -seeds of 

 cotton, flax, peanut, soja bean, almond, and sunflower. These are 

 called oil-bearing seeds. Certain fruits, such as the olive, are also 

 rich in oil. 



The ether extract of seeds may not be distributed uniformly, 

 but may be concentrated in certain parts of the seed. Thus, 

 while the entire grain of corn contains 5.5 per cent, of oil, the 



