108 MANUAL FOR SUGAR GROWERS. 



This causes the minute crystals constituting the false 

 grain to dissolve. 



It is customary to discharge only a portion of the 

 masse cuite from the pan and to take fresh syrup 

 upon the remainder ; this is known as doubling. By 

 working in this manner the size of the grain is in- 

 creased and some time is saved. Care is required in 

 conducting the operation of doubling. Some syrup 

 will get sticky after the operation is performed once, 

 while in the case of other syrups it may be performed 

 three or four times in succession. In doubling it is 

 necessary to take in the fresh syrup to open up the 

 masse cuite in the pan with the greatest care ; if the 

 syrup be admitted too rapidly false grain will result. 



If a glance be given to the diagram of the vacuum 

 pan it will be seen that the pipe C, conveying away 

 the steam from the pan, must be heated to a certain 

 extent, and the idea occurred to engineers that this 

 heat might be utilised ; the result was the invention 

 of multiple-effect evaporation, a system in which a 

 liquid is concentrated in a series of closed vessels, 

 the steam from one vessel serving to heat the liquid 

 in the next. It is evident that the pressure in the 

 successive vessels must be gradually diminished, in 

 order that the steam having the temperature of the 

 boiling liquid from one vessel may be of a higher 

 temperature than the boiling-point of the liquid in 

 the next. The following diagram of a triple effect 

 will enable the reader to follow the description of 

 the method of working. 



Juice or thin syrup is run into Vessel 1, and this 

 is heated by means of a steam-drum supplied with 



