386 CHAPTER XIX 



of the sugar in the water remaming and the purity, p, of the massecuite are 

 known. When p is unity, or when the massecuite is of loo purity, the value 

 of m is also i for all values of x. That this must be the case is self-evident. 

 Again, when /> is 0'45 and when x is o- 80 the value of m is found to be also 

 0-45. The numerical difference between p and m is the fall in purity between 

 massecuite and molasses. This figure is determined regularly as part of the 

 routine, and is used by sugar boilers as a guide in their art, and by the executive 

 as a control over the operatives. From what has already been written it 

 follows that the fall in purity is zero, both when the purity of the massecuite 

 is 100, and when it is 45 or whatever figure may be taken as representative of 

 exhausted molasses. Between these limits the magnitude of the fall will have 

 definite values and will gradually increase to a maximum as either p falls in 

 value from i, or as it increases in value from 0-45. No advantage is, however, 

 gained from calculating values oip ~ m, assigning arbitrary values to s and x, 

 since in practice s and x are not constant ; the sugar boiler will vary the value 

 of X according to the value of p, and, since s is constant at i • 8 only when :*; 

 is of the value corresponding to the production of exhausted molasses, s will 

 also vary as x varies. Assigning however values such as occur in practice to 

 s, p and X, it will be found that the maximum fall in purity which may be looked 

 for is from 25 to 30 units, and that this fall will only be obtained when p is 

 of the value 60 to 80 referred to polarization gravity purity. Finally, experience 

 has shown that from massecuites of 60 polarization gravity purity molasses of 

 30 purity (taken as the standard of exhausted molasses) can be obtained, and 

 hence it follows that from a purity of 60 downwards the fall in purity wiU 

 decrease regularly from a maximum of 30 units to zero. 



Technique of Sugar Boiling. — The actual process of sugar boiling may be 

 divided into three parts : the granulation, the growing of the crystals, and the 

 bringing up to strike. Granulation is obtained by continuing the concentration 

 of the syrup until a supersaturated solution is formed, after which sugar must 

 eventually separate, the crystallization taking place in the shape of minute 

 barely visible grains. The actual formation is usually obtained by a sudden 

 lowering of the temperature, as by increasing the injection water, by shutting 

 off steam or by introducing a charge of cold syrup. 



Dependent on the type of sugar required, the quantity of syrup used for 

 graining is varied. Evidently the less syrup taken in the smaller is the number 

 of crystals formed, and the larger will be the size of the crystals obtained 

 on the completion of the strike. One-sixth of the total quantity of syrup 

 taken in as the graining charge will afford a small crystal of side averaging 

 0*5 mm., and one-twelfth will give a grainy sugar with a side of about i mm. 

 This is the least quantity that can be used in pans, as they are usually con- 

 structed. When it is wished to still further increase the size of the crystal, 

 as in the manufacture of fancy sugars, the operation known as " washing " 

 is employed. In this process the boiler, after obtaining crystals ©f a certain 

 size, takes in large charges of syrup, juice or even water, whereby the smaller 

 crystals are dissolved, the deposit continuing on those that remain. A second 

 device to this end is known as " cutting " or " doubling," a portion of the 

 contents of a finished strike being retained in the pan to seive as a " footing " 

 or " pied-de-cuite " for the next operation. 



After having obtained the crj^stals in such quantity as his knowledge of 

 his art demands, the boiler proceeds to feed the grain by the introduction 

 of more S3'rup, which may be fed into the pan continuously or intermittently. 



