282 



CHAPTER XV 



obtained. This point is indicated by a faint pink coloration on phenol- 

 phthalein paper. The carbonated juice is now pumped to the filter presses. 

 In the earlier applications of single carbonation, it was customary to raise 

 the temperature to 90 C. before filtration, an operation no longer followed. 



Double Carbonation. The double carbonation process is conducted 

 similarly to the single one up to the breaking up of the sucro-carbonate. 

 At this point the precipitate settles rapidly, the alkalinity being from o 14 

 to 0-18 normal per 100 c.c., corresponding with the presence in the juice of 

 from 400 to 500 mgrms. of CaO per litre. At this alkalinity phenolphthalein 

 papers are coloured bright red, and so do not afford a criterion. Resource 

 is then had to " Dupont " paper, made by soaking phenolphthalein papers 

 in oxalic acid of such strength that at this alkalinity they are coloured a 

 barely perceptible pink. This determination is checked by direct titrations 

 as considered necessary. The material is now filtered and the clear filtrate 

 received in tanks, where it undergoes the second carbonation. This is con- 

 tinued up to saturation, when the juice is boiled for a few minutes to break 

 up bicarbonates and again filtered. In the earlier 

 descriptions of the process great stress was laid on 

 the importance of the first filtration in alkaline 

 medium, so as to eliminate the basic dark-coloured 

 salts. These statements referred to a process in which 

 the lime was allowed to act at 60 C. It appears that 

 when operating at 50 C. these bodies are not formed, 

 so that the advantages of double carbonation tend 

 to disappear, and indeed Harloff and Schmidt 2 dis- 

 tinctly state that the differences between the single 

 and double processes are very small. The double pro- 

 L > cess is, however, safer, and opportunity is afforded to 

 correct any error that arises in the first operation. 



De Haan's Process. 3 In this process the lime is 

 added gradually while the carbon dioxide is being 

 pumped into the juice, the other details being as 

 already described with the exception of the quantity 

 of lime used. Under these conditions the calcium 

 FIG. 1 66 carbonate is formed in a very granular condition 



and the lime used is only I per cent, on the weight of 



juice, indicating a corresponding saving in coke, dilution, and filter cloths. 

 There is also no formation of the sucro-carbonate, with consequent elimina- 

 tion of the troublesome frothing. 



Battelle's Process. 4 Battelle's process reverses the general trend of the 

 carbonation schemes by allowing the lime to act at the boiling point, whereby 

 the reducing sugars are entirely eliminated, affording the final colourless 

 products of complete breakdown. In other respects the process follows the 

 usual routine. This scheme, while giving means to obtain a superior planta- 

 tion white sugar, affords a molasses from which the sugar may be extracted 

 by the Steffen process of substitution, as is done in the beet sugar industry. 

 Up to the present this process has not been worked on the large scale, but the 

 truth of the inventor's revolutionary proposals has been demonstrated in 

 large-scale experiments made by the Hawaiian Sugar Planters' Association. 



