SUGAR BOILING AND CRYSTALLIZATIOX-IX-MOTIOX 385 



turn separated from its mother liquor. This process is repeated until a point 

 is reached where the concentration can be pushed so far that cr3sta]s and an 

 exhausted molasses result. It is at once evident that the number of operations 

 required to obtain exhausted molasses increases ^^ith the original purity of the 

 syrup. \Mth purities of 90 and over, as many as live operations may be 

 required, the last operation starting with a molasses of from 50 to 55 purity. 

 2. Reduction of Purity. This scheme, often referred to as " boiling in 

 molasses," is almost always worked in combination with crystallization-in- 

 motion processes. The material used for the reduction of purity may for the 

 moment be considered as exhausted molasses. Its effect may be looked upon 

 as mechanical, and as merelj' affording sufficient fluidity for the manipulation 

 of the verj^ concentrated purer massecuites. 



Correspondence between Purity and Concentration of Massecuites to afford 



Exhausted Molasses. 



On this basis all the sugar capable of recovery could be obtained in one 

 operation by the systematic circulation of, and introduction into the system 

 of exhausted molasses, which would appear at the end of each operation un- 

 changed in composition, but increased in quantity. The quantity correspond- 

 ing to the operation just completed is removed from the process, the balance 

 serving to reduce the purity of the subsequent boilings. The processes used 

 are, however, more complex and are described later. 



Fall in Purity. The equation (i) found above gives the value of w, or the 

 purity of the molasses obtained when the absolute soHds, x, the solubility, s, 



2D 



