60 SUGAR 



kept down as much as possible by various means, and 

 a cover to the vessel is necessary to keep back any 

 overflow, and to allow superfluous gas to be carried 

 off up a chimney. When the action is in full force 

 moderate heat is applied through a steam coil at the 

 bottom of the vessel. The frothing begins to slacken 

 and tests are applied to samples of the juice to detect 

 the right point of alkalinity, nearly approaching to 

 neutrality. At that point it is found that a sample 

 of the juice in a glass indicates a quick and steady 

 precipitation of carbonate of lime, leaving a clear 

 bright juice above. It is now ready to go to the second 

 carbonatation. Decantation of the clear juice has, 

 of late years, been given up, as it is found difficult to 

 prevent some admixture of sediment. The machine 

 called a filter press was invented, through which the 

 juice and the precipitate are forced by pressure. The 

 clear juice flows out, and the lime precipitates are 

 retained in the chambers of the press in the form of 

 flat cakes containing the lime and the impurities of 

 the juice. A perfect regiment of these filter presses 

 forms an important part of the plant of a beetroot 

 sugar factory. The clear, bright juice goes to the second 

 carbonating .vessel, more lime is added, the gas is passed 

 through the liquid until the lime is completely saturated 

 the heat being raised higher than in the former vessel, 

 and the operation is finished. The juice again goes 

 through other filter presses, and is ready for evaporation 

 and then crystallization. 



This was the process when the juice was extracted 

 in the old way by hydraulic presses. But now that 

 diffusion has become universal, even in France, and 

 furnishes a much purer juice, there is not so much 

 necessity to operate in the first instance on cold juice. 

 The juice from the diffusion batteries is already hot, 



