2go CHAPTER XVI 



great influence on sugar manufacture. Prior to this time both beet and cane 

 sugar houses specializing in white sugars had employed animal charcoal 

 nitration, and the first efforts to eliminate this agent may be traced to Melsens' 

 work. In Louisiana the application of sulphitation dates from 1860, where 

 it was used under Stewart's patent (U.S. 22590, 1859), an d at about the same 

 time it was introduced into Mauritius through the agency of leery. 



Sulphitation Processes. There are a great many ways in which sulphur 

 is used alone and in combination with other agents. Some of these methods 

 are described below. 



Raw Juice Sulphitation. In the older schemes, sulphitation was carried 

 out on the raw juice, the lime and sulphurous acid being added separately 

 to the cold juice, practice differing as to which defecant was added first. 

 In either case the same end point was aimed at, namely, a juice with an acidity 

 in terms of phenolphthalein of from 0-5 to 0-7 c.c. normal per 100 c.c. 

 When the operation is conducted on cold juice, however, a 

 rather serious trouble arises. Calcium sulphite is more soluble 

 at ordinary than at higher temperatures, and it has also the 

 property of forming supersaturated solutions. Consequently, 

 when a cold limed and sulphured juice is heated, it deposits 

 large quantities of calcium sulphite on the tubes of the heaters, 

 and also upon the tubes of the evaporator. Java practice has 

 developed a routine which satisfactorily eliminates this trouble. 

 The raw juice is heated to a temperature variously quoted as 

 70 C. to 80 C., over which region the solubility of calcium 

 sulphite is at a minimum. After reception of the hot juice in 

 open vessels, the necessary quantities of milk-of-lime and of 

 sulphur dioxide are added simultaneously. The treated juice 

 now passes through a second heater, where its temperature is 

 raised to 100 C., and thence to the settling or filter supply 

 ' tanks. In this way is avoided the coloration due to lime- 



FIG. 170 reducing sugar decomposition products following on heating 

 after addition of lime only, or inversion due to heating after 

 addition of sulphur dioxide only. 



Any deposit of scale which may form on the second heating can be sys- 

 tematically removed by alternating the flow of juice through the first and 

 second heaters. Whatever method is adopted, it seems general to use about 

 twice as much lime as would be used in ordinary lime defecation, so as to 

 obtain a sufficient bulk of calcium sulphite to carry down and entangle the 

 colloids ; at the same time the simultaneous application of lime and sulphur 

 dioxide reduces the quantities that are requisite for a good defecation. 



The action of sulphur dioxide on cane juice has been examined by 

 Browne. 5 He shows that due to the action of sulphur alone a precipitate 

 amounting to 0-3 to 0*4 per cent, on the weight of the juice is formed, and 

 the composition of this precipitate he finds as below : 



Water 4-07 4 -49 



Fat and wax 32-57 19-71 



Protein ... ... ... 23 -63 21 -75 



Ash and earthy matter ... 9-48 20 -45 



Crude Fibre 8-05 10-37 



Gums, etc 22-20 23-23 



