MANUFACTURE OF CANE SUGAR 69 



being expressed in this way ; in some cases it is extracted by 

 diffusion, which consists in immersing the cane in water, when the 

 sugar diffuses out of the cells into the surrounding water while 

 the indiffusible colloids remain behind. The crude juice is then 

 boiled with milk of lime, in order to neutralize any acid present 

 and to precipitate coagulable proteins, and is subsequently 

 treated with sulphur dioxide. After filtering, the solution is 

 concentrated in a vacuum and allowed to crystallize, 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 P er 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 and plentiful use of 

 nitrogenous and potash fertilizers the amount of sugar con- 



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

 cattle food. 



