112 THE CARBOHYDRATES 



the mother liquor being separated by centrifugalizing ; the 

 crystals may be used at once as brown sugar, or may be 

 refined. 



When the beet is used, the roots are first cut into slices 

 and subjected to diffusion, the same quantity of water circu- 

 lating through a series of vessels in such a manner that the 

 fresh water first passes over material from which most of the 

 sugar has already been extracted, and as the solution becomes 

 more concentrated, it comes into contact with material which is 

 increasingly richer in sugar. In this way the aqueous extract 

 attains a concentration of from 12-15 per cent.* This solution 

 is then boiled with lime and saturated with carbon dioxide 

 to decompose any calcium saccharosate which may have been 

 formed ; it is then filtered and again saturated with carbon 

 dioxide or a mixture of this gas and sulphur dioxide to pre- 

 cipitate the last traces of calcium, and also to decolorize it ; 

 the older process of filtration through animal charcoal is 

 thereby rendered unnecessary ; the solution is then boiled and 

 filtered and the clear filtrate is concentrated in a vacuum and 

 allowed to crystallize. The uncrystallizable residue which 

 remains is known as molasses ; a further yield of sugar may 

 be obtained from this residue by the addition of lime to the 

 cold solution or of strontia to the boiling solution whereby the 

 cane sugar in the molasses is converted into the insoluble cal- 

 cium or strontium saccharosate, which may be filtered off and 

 decomposed by a current of carbon dioxide into cane sugar and 

 calcium or strontium carbonate. The molasses are sometimes 

 fermented for the manufacture of rum or may be used for 

 cattle food ; they are also used in the manufacture of boot 

 blacking. 



By suitable methods of cultivation, seed selection and use 

 of nitrogenous and potash fertilizers the amount of sugar con- 

 tained in the beet has been raised from 10'6 per cent in the 

 period 1880-90 to about 15 per cent in the period 1900-IO, 

 and the beetroot is gradually displacing the sugar cane as a 

 source of sucrose. 



* The residue remaining after the extraction of the sugar is employed 

 for cattle food. 



