56o CHAPTER XXVII 



predetermined purities. This is effected by regulation of the quantity of 

 syrup and molasses introduced into the pan. The relative proportions depend 

 on the purity of the materials. Systematic determinations of these purities 

 must then be made. In this way the superintendent is able to instruct the 

 pan operator how many " feet " of syrup and of molasses is to be used in 

 each strike. The methods of calculation to be used are those explained in 

 Chapter XIX. The relations between contents of pans and contents of 

 storage tanks should be worked and tabulated. The pan operator should 

 also keep systematically a record of the work done on loose-leaf forms, which 

 are filed daily in the laboratory. 



Besides the routine determinations of Brix, Polarization and Purity, 

 examination of the condition of the crystals is at times useful. The recovery 

 of the separated crystals in the centrifugals is not complete, and with careless 

 operation an excessive loss may result. The determination is most readily 

 made by filtering the massecuite through glass wool and comparing the 

 analysis of the crystal-free filtrate with that afforded by the factory centri- 

 fugals. A similar analysis may be made on the molasses flowing from the 

 centrifugals. This control is of the nature of a special investigation, as the 

 systematic routine determinations of purity afford in general a sufficient 

 check. 



Entrainment Losses. — By this term is meant especially the losses which 

 occur by sugar being carried over mechanically, especially in the last body 

 of the evaporator and also in the pans. Automatic continuous samples 

 of the discharge water can be obtained by adopting the devices described 

 for juices. After obtaining the quantity of sugar, if any, in the water, the 

 volume of the latter is required in order to compute the sugar losses. 



Per lb. of steam condensed the quantity of water w required is given by 



the expression iv ~ — - — ^ where h is the total heat of the steam and 



t] and ^2 are the initial and final temperatures of the cooling water. 



The exact quantity of steam generated in the last body of multiple 

 apparatus is not known unless definite experiments are made to determine 



it. It is of sufficient exactitude to take this as — of the total evaporation 



n 



where n is the number of bodies. 



Inversion Losses. — In a well-conducted factory inversion losses should 

 not be detectable. Even if white sugars boiled from a juice with an acid 

 reaction be made, careful control may reduce these to a very small quantity. 

 The method which suggests itself for their estimation is a reducing sugar 

 balance, any increase in this material being due to inversion of cane sugar. 

 However, if the juices have an alkaline reaction, isomeric change of the original 

 reducing sugars to others with a lower reduction factor occurs, and if the 

 alkalinity be pronounced actual destruction occurs. The reducing sugar 

 balance has then a very limited application. 



Number of Analyses Necessary.^The number of analyses necessary for 

 a complete control is a matter for the judgment of the individual chemist. 

 Much unnecessary labour may be saved by judicious sampling and composit- 

 ing. Distinction should also be made between those analyses required as a 



