130 ORGANIC AGRICULTURAL CHEMISTRY 



The reaction is the same as that for the hydrolysis of starch, Experi- 

 ment XXIV, 5. 



Summary of the Carbohydrates. — The importance of the 

 carbohydrates may be emphasized by briefly reviewing them. 

 In this class we have the important food materials, starch, cane 

 sugar, malt sugar, milk sugar, glucose and fructose. Starch is 

 also widely used industrially as a sizing material and in the 

 manufacture of alcohol and glucose. Dextrin is used as an ad- 

 hesive. Cellulose has the greatest use industrially. It is the 

 constituent of such useful materials as cotton, linen, hemp, 

 jute and paper in all their various forms. Derivatives of cellulose 

 or cellulose that has been modified in form by certain treatment 

 are important as explosives (gun cotton, etc.), collodion, cellu- 

 loid, mercerized cotton and artificial silk. Also glucose and 

 glycogen are important metabolic products of the animal 

 body. When we add to all this the fact that the carbohydrates 

 are most widely and abundantly distributed in plants, we 

 realize their extreme importance in relation to agriculture. 



UNSATURATED COMPOUNDS 



While the carbohydrates are the last group of compounds of 

 any direct importance in our present study there still remains 

 an entirely distinct class of compounds which we shall briefly 

 mention. 



In the compounds which we have discussed we have con- 

 sidered representatives of all of the characteristic divisions or 

 groups, as follows : 



Hydrocarbons; simple substitution products of the hydro- 

 carbons such as mono- and poly-halogen products, and amino 

 compounds, mono- and poly-hydroxy compounds or alcohols, 

 glycerol, etc. ; aldehydes ; ketones ; mono- and poly-carboxy 

 acids; esters or ethereal salts, including the glycerol esters or 

 fats ; amides such as urea ; the related uric acid or purine com- 

 pounds ; hydroxy-acids ; amino-acids and the related proteins ; 

 hydroxy-aldehydes and the related carbohydrates. 



