290 TRANSACTIONS OF THE 



contained in the juice has therefore been proposed. A solution of sac- 

 charate of lime is thereby obtained, which is cleared of the lime by 

 passing a current of carbonic acid gas, obtained by the combustion of 

 coal, through it. This is in principle the process which is known to-day 

 under the name of carbonation. The carbonic acid acts upon the lime, 

 but has no permanent effect upon the alkalies. It is true that the sac- 

 charate alkalies are decomposed by the carbonic acid, but as the alkaline 

 carbonates are not removed, the saccharates are again brought together 

 by the heat, and are an active cause of coloring and loss. M. Basset 

 recommends the use of super-phosphate of lime in defecation, it being a 

 cheap substitute and a more effective agent than carbonic acid, eliminating 

 the lime, and at the same time destroj'ing the effect of the alkaline salts 

 which the juice contains. By some manufacturers, sulphate of alumina 

 is used to eliminate the lime. This, also, is an effective agent, and pre- 

 vents coloring, but by its use deposits are left in the juice which are 

 difficult to remove, and a sulphate of lime is produced, which must be 

 removed by filtering at twenty-six or twenty-eight degree Beaume. 



The different processes used in purifying the juice are briefly described 

 by Basset, as follows : * 



Ordinary Process. 



Elevation of the juice to the temperature of seventy-five or eighty 

 degrees centigrade; introduction and mixture of milk of lime; elevation 

 of the temperature to the boiling point; time to allow the liquid to 

 settle; decantation of the clear juice; pressure of the foam and insoluble 

 deposits; filtration of the juice through animal charcoal. 



Barnuel Process. 



This is the same as the above, with the following modifications : An 

 excess of lime is introduced so as to turn the sugar into saccharate of 

 lime. The liquid is then decanted and submitted to a current of carbonic 

 acid. The juice is then allowed to settle, and filtered as above described. 



The sulphate of alumni process has been before referred to. 



Double Carbonation. 



This is similar to Barnuel's process, with this exception, that after the 

 first action of the carbonic acid a new quantity of lime is introduced, 

 and the juice is again subjected to the carbonic acid. Decantation and 

 filtration as above described. 



Troubled Defecation. 



Elevation of the juice to the temperature of seventy-five or eighty 

 degrees centigrade; introduction of lime; then, without decantation, the 

 introduction of carbonic acid. Decantation, pressure of the deposits, 

 and filtration of the juice through animal charcoal, as before described. 



Concentration. 



The purified, filtered and decolorized juice is concentrated by*the 

 action of heat, which causes it to lose its excess of water, and brings it 



* Etudes surl'Exposition de 1367. 



