Sugar 



97 



A ROW OF CENTRIFUGAL MACHINES FOR SEPARATING SUGAR CRYSTALS FROM MOLASSES 



cisterns. After remaining here for two or three days the whole mass, now consisting of 

 sugar crystals and molasses, is dug out and put into sacks or hogsheads to drain, the 

 molasses or treacle draining away and being collected elsewhere, whilst the sugar remains 

 behind. This is in brief the most primitive way of manufacturing sugar on a considerable 

 scale. It is in some respects very wasteful. Evaporation in open pans necessitates high- 

 temperatures being attained, and consequently the amount of inversion which takes place is 

 greater. The separation of sugar crystals and molasses is very imperfect. One point in its 

 favour is that it yields excellent molasses, but whether this is sufficient to compensate 

 for loss in other directions is a question to be settled according to special conditions on the 

 estate. From the sugar-producing point of view improved molasses means loss of possible 

 sugar. 



We will now turn to indicate in outline more modern methods, which have been adopted 

 mainly from the rival industry as competition between the two increased. 



The loss of crystallisable sugar owing to its being inverted at the high temperatures neces- 

 sary when the syrup is evaporated in an open vessel was overcome by making practical use 

 of the well-known physical law that liquids boil at a lower temperature if the atmospheric 

 pressure is reduced. The vacuum pan was invented in which the partially evaporated syrup 

 underwent its final concentration under very low atmospheric pressure. Accordingly it " boiled " 

 at a much lower temperature and there was correspondingly little loss from inversions. Still 

 further advances led to the replacement of the whole series of tayches by a series of vessels, three 

 being usually employed, and the set known as a " triple effect." Not only do the triple effect 

 and vacuum pan economise sugar, but they also economise fuel, and they are used in all large 

 modern factories. They are not heated at all directly over a fire, but internal steam coils are 

 made use of. The vacuum pan is made with small glass windows at the sides : on looking 



