CHAPTER XV 



The Carbonation Processes 



In the carbonation processes a very great excess of lime is allowed to act 

 on the juice, the excess of lime being eventually removed as carbonate 

 through the action of carbon dioxide gas which is pumped through the 

 material contained in special tanks. Actually the schemes would be more 

 rationally termed " excess lime processes," as the effects produced are 

 essentially due to the hme, the role of the carbon dioxide being only secondary. 



The inception of these processes is to be found in the beet sugar industry, 

 where an excess of lime was thus first removed by Scatter in Germany in 

 1843. He was followed by Kiihlmann and by Rousseau, who described the 

 single carbonation process in patent 14318, 1858. The double carbonation 

 process is due to Possoz, Perrier and Cail in France, and to Jelinek and Frey 

 in Austria. The three first-named inventors described the process in patents 

 1861 of 1859 9-^d 28 of 1870. 



The system was first adapted to cane sugar manufacture by Pellet, and 

 was first used in the cane sugar industry in Java at Wonopringo and 

 Djattiwangi in 1878. It was used at an early period at Almeira in Spain, and 

 as Boivin and Loiseau's " hydro-sucro-carbonate " process in Australia in 

 1870. It has been sparingly used in the Hawaiian Islands. At the present 

 time some twenty factories in Java, together with at least one each in Egypt 

 and British India, operate the process. 



Carbonation processes are only used where a white sugar for direct con- 

 sumption is made, and as now conducted carbonation is combined with 

 sulphitation, the application of which is discussed in the next chapter. 



Chemistry of the Processes.^ — In Chapter XIII it was stated that when a 

 juice has been limed so far that it is just alkaline to phenolphthalein, no 

 further precipitation takes place with the continued addition of lime, and 

 it would therefore appear to be irrational to add more lime still. When, 

 however, there is a great excess of lime, which is afterwards precipitated in 

 the juice, the calcium carbonate formed carries down mechanically much of 

 the colouring matter not yet precipitated, as well as much of those indefinite 

 bodies referred to as " gums." A secondary, though very important, effect 

 is the ease with which such a material can be filtered, due to the presence of 

 the granular precipitate. 



Cane juices normally contain a considerable quantity of reducing sugars, 

 and the action of hme on these bodies is of great importance. At tempera- 

 tiires not above 50° C. the main product of the action of hme is lactic acid 

 appearing in the juice as lactates. These salts are stable and colourless 

 and do not form basic combinations. As the temperature of reaction rises, 



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