CANE SUGAR. 



Carbonating Tanks. The carbonating or saturation tanks, Fig. 

 are made either rectangular or circular ; the latter form is preferable as tending 

 to a more uniform distribution of the carbon dioxide. They are often provided 

 with an iron lid, to which is fitted a short chimney. Where this device is not 

 utilized, the froth is broken up by means of a jet of steam brought to play 

 upon the surface. A mechanical arrangement, consisting of a scraper passing 

 over the surface of the juice, is sometimes used, and a stirring device, as shown 

 in Fig. 18, is also employed. 



The height of the liquid undergoing treatment varies in practice from 

 4 to 9 ft., and owing to the frothing the vessels are not filled to within 1 or 2 



FIG. 149. 



ft. of the top of the containing vessel. No useful purpose is served by 

 decreasing the height of liquid, as if too low there is danger of carbon dioxide 

 passing away unutilized. 



To distribute the gas uniformly through the liquid various devices are 

 used. The commonest method is to use a perforated coil, for which may be 

 substituted a perforated disc or drum : any method which secures uniform 

 distribution of gas is effective. In addition to the gas distributing coil, steam 

 coils are provided for boiling the juice ; an allowance of 1 square foot heating 

 surface for every two gallons capacity is sufficient. 



266 



