392 CHAPTER XIX 



4. The third molasses are boiled blank and discharged into larger 

 receptacles, which often take the shape of wooden vats or iron tanks. In 

 these containers, which often, and improperly, hold two or three pan strikes, 

 the massecuite is allowed to granulate for a period of two or three months, 

 after which a low grade sugar and fourth molasses is obtained. The sugar is 

 treated as in that obtained in the third boiling, and often the molasses 

 obtained are commercially exhausted. 



5. In the case of exceptionally high purities a fifth stage may be necessary 

 to obtain a complete exhaustion. In such a case the material may be carried 

 on from year to year, remaining in the containers for twelve months. 



A routine like that described finds little use now, the objections to it 

 being : I. The very large storage room required. 2. The inconvenience 

 of handling so large a proportion of low grade material. 3. The repeated 

 passing through both pans and centrifugals of both low grade sugars and 

 molasses. 4. Excessive labour. 5. Capital locked up in unmarketed 

 sugar. 6. Heat and material losses inherent to the system. 



The first variation from the system of repeated boilings with separation 

 of the crystals in stages was obtained by the reduction in purity of the first 

 massecuite by boiling in part of the molasses on hand, instead of boiling 

 them separately. In this way in one operation in the pan and centrifugals 

 the syrup could be separated into crystals and molasses of such a purity 

 as would have required two or more operations if the molasses had been 

 treated separately. This scheme did not, however, eliminate the final 

 boilings which entail so much time and storage besides affording an inferior 

 sugar. Eventually the process of crystallization-in-motion was devised and 

 now finds a place in all modern factories. 



Crystallization-in-Motion. For very many years past the old West 

 Indian houses have been accustomed to periodically disturb the magma 

 of crystal and molasses which had been struck out into coolers. The hand- 

 operated appliances used for this purpose were known as oscillators, and this 

 process had in view the acceleration of the deposit of sugar. On the larger 

 scale the first attempt to work thus seems to have been made by Vanaertenryk 

 at Lembeek in Belgium, in 1869, wno applied motion to massecuites 

 boiled blank. Crystallizers in the modern sense of the term were first used 

 by Bocquin and Lipinski in Russia in 1880 ; but the real starting point of 

 the process is due to Wulff, who in 1884 gave a rational theory of the physics 

 of the process. He proposed to boil lower-grade material string-proof, and 

 to add a predetermined quantity of sugar crystals to the supersaturated 

 mass in the receivers ; on cooling in motion the sugar deposited on the 

 crystals and the low grade sugars were eliminated. It is easy to see how this 

 scheme can be developed from the theory given in this chapter. A second 

 early proposal was that of Bock. In this scheme a strike boiled from straight 

 syrup and separated into crystals and molasses only as regards two-thirds 

 of its weight. The resulting molasses were boiled string-proof and struck 

 on to the remaining third, the whole being then cooled in motion. It was 

 expected that exhausted molasses would result. It is easy to see that no 

 fixed proportions for the division of the original strike can be laid down, 

 and that this must depend on the initial purity. In 1890, Steffen introduced 

 the systematic return of molasses made with due regard to purity, and this 

 system is the basis of the present methods of working. 



All these schemes had their inception in the beet sugar industry, and it 



