THE CONTROL OF THE FACTORY 557 



which must be removed from an original material of purity j to afford a 

 residue (molasses) of purity m. 



In the use of this formula all purities must be referred to one and the 

 same basis, i.e., all must be either absolute, gravity or refractive purities, 

 and, further, the formula is correct only with determinations of sucrose and 

 not with polarizations. 



As a basis of reference the writer prefers gravity purities, on the grounds 

 of both accuracy and ease of execution. The refractometer is of lower 

 sensibility and there are inherent sources of error in the determination of 

 dry matter, especially in low grade cane-sugar products. 



The scheme put forward by the writer for determining gravity purities 

 for control purposes is best shown by an example. The syrup or finally 

 purified material before the abstraction of sugar is, for example, analysed 

 at 15 per cent, gravity solids, and is of 85 purity. 



It therefore contains 2 25 per cent, non-sugar. The raw sugar contains 

 3 per cent, of non-sugar. A determination of the gravity solids should there- 



2 * 2^ 



fore be made at a concentration of 100 X - or 75 per cent. As this is 



at a greater concentration than is possible, the determination is made at a 



concentration of about 60 per cent, with the known admission of a small error. 



Similarly, if the molasses is known to be of approximate composition, 



water 20, sugar 30 per cent., non-sugar 50 per cent., the determination is 



2 *25 



made in a concentration of about 100 X or 4-5 per cent. 



As an actual example of the use of this formula in control the following 

 example may be given. 



Juice contained 1023 4 tons sucrose, of which 8 4 tons was lost in the press 

 cake, leaving 1015-0 tons in the syrup, which was of gravity purity 85*32. 



The raw sugar obtained was 950-8 tons, containing 96-32 per cent, 

 sucrose or 915 8 tons sucrose. Determined at a concentration of 60 per cent, 

 the gravity solids in the sugar were 99-73 per cent., whence the gravity 

 purity was 96-58. The gravity solids in the molasses determined in 4 per 

 cent, concentration were 90-43, the sucrose per cent, was 36-44, giving a 

 gravity purity of 40-41. The value of 



s (j m) . 96-58 (85-32 40-41) 



100 X'^r is then: 100 X g J ; ? { = 90-53. 



j(s-m) 85-32 (96-58 - 40-41) 



That is to say the possible recovery of sucrose as deduced from the actually 

 observed control analyses is 90-53 per cent, of the 1015-0 tons obtained as 

 syrup or 918-9 tons. The actual recovery was 915-8 tons, indicating a loss 

 of 3 i tons in the operations of boiling, crystallizing and centrifugalling. 

 By the rational use of the s, j, m, formula as developed above a control over 

 and an examination into the processes in the boiling house can be obtained. 

 A divergence between the computed and observed results may be due to 

 actual losses, to incorrect weighings or to inexact analyses. 



If such a divergence should arise, it is the duty of the chemist to locate 

 the cause and of the executive to remove it. 



The sugar lost in the press cake may be regarded as available or not, 

 depending on the point of view of the chemist. The writer prefers to regard 

 it as available and to refer calculations to the sugar in the mixed juice, 

 using, however, for j the value determined in the syrup as representing the 



