32 



THE CUBA REVIEW 



A modification of this process is one in 

 which the clear liquor, after filtration, is made 

 slightly acid by being ''sulphured," and it is 

 claimed that by this process, which is called 

 the "acid thin juice" process, a much brighter 

 sugar results than with the ordinary car- 

 bonation process. 



In the double carbonation, the process of 

 carbonating is divided into two stages. The 

 juice is heavily limed, as in the single car- 

 bonatation process, and is then heated to 140 

 deg. F., at which stage carbonic acid gas 

 is added until a slight but definite alkalinity 

 is left. It is then filtered through filter presses 

 and the filtered juice is again treated with 

 carbonic acid until the juice is neutral. The 

 juice is now boiled and filtered. 



A modification of this process is that of 

 Battelle, in which the juice is raised to the 

 boil after the lime is added, in order to destroy 

 the glucose. It is now carbonated to neutral- 

 ity, and filtration effected. The clear juice 

 is now slightly limed again, carbonated 

 to neutral point, boiled, and filtered. The 

 benefits claimed for this process are: firstly, 

 that there is no danger of discoloration of the 

 juice from partial glucose destruction during 

 carbonatation; and, secondly, that the 

 Steffen process can be used to obtain the 

 sugar from the molasses, which are practically 

 completely exhausted of sugar by this means, 

 the Steffen process treats the molasses with 

 dry lime, forming an insoluble saccharate of 

 lime, which is filtered and used for clarifica- 

 cation purposes, the sugar in the saccharate 

 re-entering the juice in this way. 



In the De Haan modification of tfip double 

 carbonatation process, the necessary alkaline 

 reaction of the first carbonatation is obtained 

 from the commencement by adding the lime 

 and carbonic acid at the same time to a 

 continuous flow of juice. The objectionable 

 frothing is thus avoided. 



The above gives an outline of the various 

 clarification processes in vogue in the 

 present-day manufacture of white sugar direct 

 from the cane juice. The other part of the 

 manufacture which plays an important part 

 in the white sugar manufacture is the method 

 of treatment of the massecuites, and the great 

 imderlj'ing principle is that of double curing. 

 In this the massecuite is cured without the aid 

 of water in one set of centrifugals, the sugar 

 made into a magma with washings from the 

 second curing, and cured again in a second set 



of centrifugals, in which the necessary wash- 

 ing and steaming is done, the resultant white 

 sugar going to a drier, while the washings go 

 partly to form the magma mentioned above, 

 with the balance back to either the syrup or 

 the clarified juice. The drier prevents any 

 likelihood of the sugar deteriorating in a 

 moist climate. 



The great advantages of this system are 

 that the molasses proper are kept separate 

 from the washings and steamings, while at 

 the same time the formation of the magma 

 greatly facilitates the subsequent washing 

 of the sugar. It may he mentioned that the 

 molasses massecuites, which are invariably 

 built on grain from syrup, are treated in the 

 same manner. 



An important point in connection with the 

 subject under review is that of the relative 

 cost of the clarification processes. This, of 

 course, must vary according to the local 

 price of the chemicals employed and of 

 labor. As a guide, the following figures, 

 given by Dr. Prinsen Geerligs,* are of value 

 as representing the Java conditions. In these 

 the cost of the ordinary sulphitation and 

 double carbonatation are compared. Taking 

 1,000 tons of canes, the cost of chemicals and 

 labor for the clarification departments are: 



Sulphitation Carbonatation 

 Chemicals. .. £ 5 12 11 £31 17 



Wages 1 16 10 6 3 5 



Total 7 9 9 38 5 



Or if nine tons of canes are taken to the ton 

 of sugar, the relative cost would be a little over 

 1/8 per ton and 8/6 respectively, a difference 

 of nearly 7 /-per ton against the carbonatation 

 process. 



Another matter of the greatest importance 

 is the effect of the process upon the extraction 

 of sugar. In this connection Dr. Geerligs 

 again gives information, also from Java. 

 Taking the sulphitation yield as 100, he gives 

 that of double carbonatation as 100.32 of 

 De Haan's process 100.64, and of the Bach 

 sulphitation process 100.96, a difference dis- 

 tinctly in favour of the latter. 



There is one advantage in the sulphitation 



ystem which must not be overlooked, and 



hat is that at any moment a sulphitations 



plant can be turned on to the make of grey 



sugar if required in the ordinary manner. 



■ *"The Manufacture ofWhite Sugar," Norman Roger, 

 2 St. Dunstan's Hill, E. C. 



