90 Agricultural Chemistry. 



surface of the tube, while the remaining blackened or charred 

 portion denotes the presence of carbon. Glucose is a product of 

 the decomposition of all higher carbohydrates. It is about two- 

 thirds as sweet as common sugar. 



5L^ Levulose or fructose is a mono-saccharide of the samp general 



Vv/Vcomposition as dextrose and has many properties in common with 



it. The two sugars are commonly associated in fruits. Levulose 



is abundant in honey where it exceeds the amount of dextrose. 



the two forming about 75 per cent of the product. 



No other hexose-sugars occur free in plants, but galactose is n 

 compound of this class. It is formed by hydrolysis or addition 

 of water to a group of poly-saccharides, called galactans, which 

 occur in plants. 



Di-saccharides are represented in the plant kingdom by two 

 sugars. Sucrose, or cane and beet sugar, occurs in many plants, 

 notably in the juice of sugar cane (16 to 18 per cent), in the 

 sugar beet (10 to 18 per cent) , and in the sap of the sugar maple 

 (about 90 per cent of the solids). The sweetness of the sap of 

 corn and sorghum stalks and of peas and other seeds is due to 

 appreciable amounts of sucrose. This sugar differs from the 

 mono-saccharides in that it crystallizes readily, and this property 

 is taken advantage of in purifying the commercial product. By 

 the action of the enzyme invert in, which occurs in yeast, sucrose 

 is converted into equal parts of dextrose and levulose, hence the 

 designation ' ' di-saccharide. ' ' 



This process of ' 'Inversion * ' may be accomplished also by boil- 

 ing sucrose with dilute acids, the product by both methods being 

 known as "invert sugar. " The change involves the addition of 

 one part of water to each part of cane sugar and this reaction 

 characterizes the inter-relations of carbohydrates in general, 

 which are largely dependent upon differences in content of the 

 water-forming elements. 



Maltose or malt sugar, is a di-saccharide occurring in small 

 amounts in seeds. Its amount is considerably increased as a 

 result of germination, in which the enzyme known as diastase 

 converts starch to dextrines and maltose. Crystallized maltose 



