68 SUGAR 



above the top of the steam drum, but not far enough 

 to incur the danger of boiling over. The final vessel 

 of this triple-effet is connected with the air pump 

 and condenser. Low pressure steam enters the drum 

 of the first vessel, the thin juice boils and begins to 

 thicken. It is transferred to vessel No. 2 ; vessel No. 1 

 being charged with fresh juice. The steam from the 

 evaporation of the juice in No. 1 goes into the steam 

 drum of No. 2, and boils the partially thickened juice. 

 There is a slight vacuum in No. 2 ; and even in No. 1 

 a slight vacuum is created by the rapid condensation 

 of its steam in the drum of No. 2. In No. 3, the vessel 

 nearest to the pump and condenser, the vacuum is greater. 

 The still thicker juice in No. 2 goes into No. 3 ; No. 2 

 is filled from No. 1, and fresh thin juice goes into No. 1. 

 The triple-effet is now in full work, which goes on 

 continuously. The steam from the boiling juice in 

 No. 2 goes into the steam drum of No. 3, and not only 

 boils the juice there, but improves the vacuum in No. 2 

 by its rapid condensation. The transfer of juice from 

 vessel to vessel, and from the thin juice tank to the first 

 vessel, takes place every time that a charge of sufficiently 

 thick juice is drawn from No. 3 to be cleaned and go to 

 the vacuum pan. The arrangements for drawing off 

 the water of condensation, and the precautions against 

 loss of sugar by the carrying over of bubbles of juice 

 in the steam, need not be detailed, nor the cleaning 

 of the copper tubes, and many other necessary operations 

 connected with this complex apparatus. 



Here we have not only a great saving of steam, but 

 also a complete method for avoiding, as much as possible, 

 any injury to the sugar when the juice becomes thick 

 and, therefore, more sensitive. But the juice, which 

 was perfectly clear and bright when it entered the triple- 

 effet, loses its brightness as it passes through the process 



