CHAPTER XII 

 The Diffusion Process 



In the early part of the nineteenth century a German professor, Goettling, 

 proposed to extract the juice of the beetroot by systematic washing, and 

 his scheme was operated at Ka-rlsruhe, by Haber and Schutzenbach. In 

 France the earUest pioneer of this process was Matthieu de Dombasle, whose 

 French patent is 7981 of 1831. The earhest British patent and the first one 

 mentioning the cane is that of Watson (7124, 1S36) which describes a one-cell 

 coimter-current process. Constable's British patent, communicated to him 

 by ]\Iichel. is 10171, 1S44, and it describes a process in which the cane is 

 transferred in perforated baskets from ceU to cell. This patent correctly 

 describes the mechanism of diffusion through a permeable membrane, and is 

 the one which was unsuccessfully operated in Guadeloupe by Bouscaren 

 about this time. The actual introduction of diffusion as a commercial 

 process is due to Robert, the manager of a beet sugar factory at Seelowitz, in 

 Austria. His British patents are 594 and 31S7 of 1866, taken out by ^linchin, 

 who operated diffusion successfully at Aska, in India. 



From the time of its first successful operation, the diffusion process 

 became rapidl}* established in the beet sugar industry, and its operation 

 remains now as originally executed. The only developments have been 

 some attempts to put uito operation continuous diffusion processes, such as 

 those of Kessler (British patent 15355 of 1902) and of Rak (British patent 

 16905 of 1901). The latter is in use in a few factories. 



In a diffusion process proper, the plant ceU is not ruptured, and advantage 

 is taken of the property possessed by crystalloids of passing through a ceU 

 wall, or membrane, when water or a solution more dilute than that contained 

 in the ceU is in contact with the exterior of the ceU waU. In this way the 

 bodies of a colloid nature which do not possess this property are retained 

 within the cell. Independently of diffusion through a ceU wall, all solutions 

 in contact tend to become of equal concentration, and the process is physi- 

 call}- of the same nature as diffusion, such an action obtaining when the ceU 

 wall is ruptured. 



This property occurred in the older processes, such as that of Dombasle, to 

 which the term " maceration " ■\\as originally applied, and. this term or some 

 equivalent such as " lixi\'iation," should be appUed to those processes which 

 deal with comminuted material such as bagasse, since in the absence of a 

 ceU wall or other permeable membrane diffusion proper does not obtain. 



In the sugar cane industry numerous plants were erected in Spain, 

 E&>T^' Louisiana, ^lauritius, Brazil, Demerara, Java, Hawaii, and the \\'est 

 Indies. Yery few of them now remain, and most of those that were erected 

 met ^\-ith financial disaster. The causes which led to failure were both 

 technical and economic, and may be briefly summarized : — 



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