176 



SUGAR. 



" The property of sulphurous acid gas, or of salts containing that 

 gas, such as the bisulphite of lime, in preventing or arresting fer- 

 mentation, and in bleaching vegetable substances, is well known. It 

 seems to have been applied to the manufacture of sugar from cane 

 juice as early as 1838, when Mr. E. StoUe took out a patent for dis- 

 colouring saccharine matter by sulphurous acid gas instead of animal 

 charcoal ; and subsequent patents have been taken out in 1849, 1850, 

 1857, and 1862, for similar purposes. But it does not appear that 

 any marked success has attended the use of the gas, though it is in- 

 comparably cheaper than the bisulphite of lime, which at present is 

 largely employed in the British West India colonies. It may be that 

 the latter substance finds favour on account of its not requiring 

 special apparatus for its application ; but I am inclined to think that 

 sulphurous acid gas has failed from two causes. In the first place, it 

 has to be applied quite as carefully as the lime used in ordinary tem- 

 pering. Being extremely soluble, juice will take it up to the extent of 

 thirty-three times its own volume, and hence a great excess is easily 

 and imperceptibly added, only to require neutralizing again by lime, 

 which forms sulphite and bisulphite of lime ; the latter being wholly 

 soluble in the weak cane juice, but is in part changed, at the expense 

 of the atmosphere, into the sulphate, which, although soluble in about 

 four hundred and fifty volumes of hot water, is deposited rapidly on 

 the surfaces of the concentrators and vacuum pans, rendering them 

 inefficient, and extravagant in fuel. In the second place, the gas has 

 always been tried at existing factories, most probably with very 

 defective and slow concentration ; hence the juice, which if quickly 

 concentrated — not, however, in vessels heated by dii-ect fire, as in 

 ' taiches ' and concretors — would have made white sugar, has been 

 degraded till all the benefits of the gas are lost. The Aba factory, 

 it is believed, is the only one ever built expressly for the use of 

 sulj)hurous acid, and hence the success which was immediately 

 attained. 



" In the simple clarification with lime, great care should be taken 

 to add the exact quantity necessary to neutralize the organic acids 

 in the juice. The salts of lime then formed — chiefly acetate — are all 

 soluble, and are not deposited if concentration follows rapidly ; but 

 if there is an excess of lime, or long exposure to the air, the carbonate 

 is formed at the expense of the atmosphere, and becomes very trouble- 

 some. At Bene Mazar, last crop, the clarification was constantly 

 under European supervision, and so carefully done that, at the end of 

 the season, there was no deposit whatever, either in the triple-action 

 tubular concentrators or the vacuum pans ; and, as excellent white sugar 

 was made, it is presumable that the correct quantity of milk of lime 

 was used. This varied between 1 J gallon to 2^ gallons, at 10° Beaume, 

 corresponding to from 1^ lb. to 2| lbs. of caustic lime, or say, an 

 average of 2 lbs. of caustic lime per clarifier of 353 gallons. At Aba, 

 during my experiments, J lb. of sulphur was actually consumed for 

 450 gallons of juice ; but this quantity, in consequence of the imper- 

 fect arrangements for ' gassing,' was greatly in excess of what was 

 necessary for clarification. Laborator;^ experiments seem to indicate 

 that about lb. per 450 gallons will be sufficient. The lime required 



