426 MONTHLY JOURNAL OF AGRICULTURE. 



We do nol intend to examine here the mechanical processes, the object of 

 which is the extraction of the juice from the cane. We will not include in our 

 present investigation those advantages which consist in an increased yield of 

 juice — advantages which are not to be neglected, but in regard to which we have 

 still experiments to make, and to the study of which we are devoting our whole 

 attention. 



As for the chemical and evaporative processes, the object of which is to obtain 

 from the juice extracted from the cane the greatest possible quantity of sugar, in 

 regard to which at this day everything is known, they come entirely within the 

 sphere of investigation which Ave have proposed to ourselves. 



Chemical Processes. 



The operations acknowledged now as indispensable in the treatment of the 

 juice are — 1st, the defecation by means of lime ; 2d, the filtration tlirough ani- 

 mal charcoal in large masses. These two indispensable processes give each other 

 mutual aid. 



Defecation in double-bollom Kettles, heated by Steam. 



The first point in the manufacture of sugar is a good defecation, Avithout which 

 all subsequent operations proceed badly. The defecation should be so made as 

 to furnish juice perfectly limpid, exempt from any milky appearance. This de- 

 fecation is accomplished, in the old as well as in the new method, by means of 

 lime. Brought in contact with the juice, lime neutralizes its acid, and concretes 

 the mucilaginous matter given out by extraction. In the Colonies, lime is used 

 in quantities too small to effect the separation of the heterogeneous matter, the 

 presence of which is essentially injurious to sugar. It is well known there that 

 defecation is more perfectly accomplished by larger doses of lime ; but it has also 

 been remarked that syrup defecated with an excess of lime cooks badly ; hence 

 it is used sparingly and with caution, and vegetable matters are allowed to re- 

 main in the juice, which are highly prejudicial, by converting a portion of the 

 sugar into molasses. In the new process, a quantity of lime is employed, suffi- 

 cient to effect a perfect defecation, without regard to what may happen to the 

 syrup in the after processes. Our Derosne has employed in Cuba Ik measures 

 of lime per kettle, instead of 21 employed in the common process. 



The excess of lime which may remain in the juice is immediately eliminated 

 after defecation by its passage through animal charcoal. This is one of the ben- 

 eficial effects of this agent in the manufacture of sugar. The result is that the 

 juice, well defecated with a sufficiency of lime, and then filtered, is nothing more 

 than sugar and water, which only requires to be evaporated and cooked in a suit- 

 able manner to be converted into sugar containing the least possible quantity of 

 molasses. 



The kind of kettles employed in the defecation is a point of much importance. 



Defecation by naked fire* (fire directly applied to the bottom of the kettles), 

 after the fashion in the Colonies, and as was practiced in the first stages of the 

 beet-root manufacture, is very objectionable; because the moment the lime en- 

 ters into combination Avith the extraneous matters in the sugar, the poAver should 

 exist of immediately arresting the ebullition, so that the liquid may be at rest. — 

 This is accomplished in double-bottom, semi-spherical kettles, healed by steam. 

 By means of a stop-cock, the action of the caloric and the ebullition are immedi- 

 ately arrested, and the scum separates in two layers, one of Avhich rises to the 

 top of the kettle ; and the other, Avhich is heavier, falls to the bottom. In the 

 intermediate space is a licpiid perfectly clear, Avhich is draAvn ui\' by means of a 

 cock connected Avith a tube running uj) through thu M-diuient into the clear liquid. 



Ill ilic dcfc.;rtiion by n.ikcd tiiL", wlien the moment of coiubiiiation arriviw. ilic 

 fire has to be put out or damped, the eiiullilion still continuing for a longer or 

 shorter time, during Avliich tiie scum breaks and mixes Aviili the mass of ihe 

 juice, thereby rendering it impossible afterAvard to give it clearness or limpidity. 

 This is one of the principal causes of defective manufacture. The extraneous 

 substances remain in the mass during the Avhole lime of evaporation and cooking, 

 and decompose more or less of the sugar. Hence the necessity in the Colonies 

 of continually skimming the kettles ; Avhereas in the ncAV system, once the juice 



* In contrfidistinclion to the a:.'plicati()n by sleaiii. wliicli ia iiidirciU. 



(85S) 



