THE EXTRACTION OF THE JUICE BY MILLS 233 



bagasse." This process is variously known as imbibition, maceration, 

 lixiviation, saturation, or dilution.* 



The water used in imbibition may be applied in various ways, and of 

 these there may be distinguished : — i. Simple Imbibition where water only 

 is used at each of the wet crushing units, the process being classed as single, 

 double, treble, etc., simple imbibition depending on the number of units ; 

 and 2. Compound Imbibition, where water is only used at the last mill, the 

 dilute juice therefrom being used as the diluent before the penultimate 

 mill, that from this mill going to the antepenultimate mill, and so on. A 

 single compound process indicates the use of only one wet crushing unit, 

 and is hence the same as single simple imbibition. Double, treble, etc.. 

 compound imbibition imply the use of two, three, etc., wet crushing units. 



It will be apparent that the number of units employed in the dry crushing 

 has no effect in determining the type of process emploj^ed, the break in the 

 continuity of the schemes occurring with the addition of water or other 

 diluent. Experience has shown, however, that to obtain a satisfactory 

 dry crushing not less than two three-roller units, acting in combination 

 with some preparatory device, are necessary ; accordingly, a double conl- 

 pound installation will often consist of a two-roll crusher, followed by four 

 three-roller mills. Such a combination is usually referred to as a crusher 

 and twelve-roller tandem ; actually, however, the crusher and first six 

 rollers may be regarded as but one unit. 



Let the weight of canes be unity, and let the fibre per unit weight of cane 

 be/, -whence the weight of juice is i — /. 



Let juice be expressed in the dry crushing until the fibre becomes m 



per unit weight of bagasse. 



f 

 Then — = weight of bagasse per unit weight of cane. 



f •ryt / 



I — — = '- = Weight of juice expressed per unit weight of cane. 



m m 



m~ f 



m (i— •/) 



m 

 f (i — m) 



= Weight of juice expressed per unit of jiiice in cane. 

 = Weight of juice in bagasse per unit weight of cane. 

 = Weight of juice in bagasse per unit of juice in cane. 



m (I -/) 



Generally m = 0-50 is indicative of superior work, and this constant 

 value will be adopted throughout this section when any numerical calcula- 

 tions are given. As f increases so also does the value of—, while that of 



•^ m 



— decreases. Thus with / = o-i and m =0-5, the value of the latter 



m 



or the weight of juice expressed is o-8o, a figure which falls to o-68 when 

 /"rises to o • 16. Evidently in both cases the crushing is equally good although 



♦ Maceration was the term used by Dombasle in 1831 in connection with his process for the systematic extrac- 

 tion of beets. When the systematic extraction of sliced beets was established by Robert about 1860 the term 

 diffusion was properly employed. Maceration as applied to cane milling in the processes usually followed is a mis- 

 nomer, and though in general use wUl be here discarded in favour of imbibition, the term alwaj^ used by French 

 writers, and one which correctly describes the process. Dilution indicates the effect rather than the means while 

 saturation has no proper significance in this connection. Lixi\iation is also inappropriate and is used only In 

 reference to the Perichon process, confined to Egypt. 



