FOODS 103 



sake of completeness. These are raffinose or melitose 

 (tri-saccharid), arabinose (pentose), and mannite, dulcite, 

 and sorbite (hexahydric alcohols, hence better called 

 mannitol, dulcitol, and sorbitol). 



The carbohydrates are distinguished from one another 

 not only by their chemical constitution but by their relative 

 sweetness, their source, their power of crystallization, 

 their oxidation products, their power of reducing Fehling's 

 solution, their action on polarized light, their reaction to 

 the yeast and other ferments, and other tests. 



Commercially, sugar is obtained from the sugar cane 

 (West Indies), beetroot (Western Europe), the maple tree 

 (Canada and U.S.A.), various palm trees, such as date palm 

 (India), sago palm (Ceylon), Palmyra palm (South America 

 and Australia), a grass plant called sorghum (U.S.A.), and 

 maize or Indian corn (Mexico). These plants all yield 

 the Sugar known under the various names of sucrose, 

 saccharose, cane sugar, beet sugar, etc. Sugar is soluble in 

 i part of its weight of water at 15 C., in part in cold 

 water, and in all proportions in boiling water. It dissolves 

 with difficulty in alcohol. Its sp. gr. is 1-606. Its aqueous 

 solution is dextro-rotatory, its specific rotatory power at 

 20 C. for sodium light being A,, = + 66-5. It melts at 

 1 60 C., and on cooling forms an amorphous glassy mass 

 known as " barley-sugar," which in time loses its trans- 

 parency and becomes crystalline. At 190 to 200 C. it 

 changes to a brown non-crystallizable mass called caramel, 

 which is used for colouring liquids. It does not reduce 

 Fehling's solution nor ferment with yeast. When boiled 

 with dilute acids it is decomposed into dextrose and 

 laevulose, both of which reduce Fehling and ferment with 

 yeast, but rotate the plane of polarized light in opposite 

 directions. The laevulose has the greater rotating power, 

 with the result that the solution has now a laevo-rotatory 

 action, and is hence called " Invert Sugar." Cane sugar 

 forms compounds with metals, metallic oxides, and salts, 

 and these are named saccharates or sucrates, such as sodium 

 sucrate, chloride of sodium sucrate, and lime sucrate. 

 Cane sugar crystallizes in large monoclinic prisms. Boiled 

 with nitric acid it oxidizes to oxalic and saccharic acids 

 and inactive tartaric acid. 



