AMERICAN BEET SUGAR. 41 



peller arms constantly revolving, which is termed a "mixer." Attached to and 

 directly underneath the mixer, are 8 centrifugals, 40 inches diameter. 



THE CENTRIFUGALS. These machines consist of revolving "baskets" sur- 

 rounded by safety curbs ; the baskets are lined with a finely perforated brass 

 screen. About 500 pounds of the " magma " is taken into a centrifugal at a time ; 

 the machine is caused to revolve by means of suitable belts and pulleys till it 

 attains a velocity of 1000 revolutions a minute ; the centrifugal force, which is 

 about 40 pounds per square inch, throws the " magma " to the sides, the screen 

 holding the sugar back, the molasses is thrown off through the screen till it strikes 

 the sides of the safety curb, flows off in a pipe at the bottom, and is collected in 

 tanks for further manipulation. 



After the "magma" has been in the revolving centrifugal a few minutes, it is 

 entirely freed from syrup, then a jet of water is sprayed on it to remove the last 

 trace of molasses, the machine is stopped, and the sugar falls through an opening 

 in the bottom into a conveyor which carries it to an elevator connected with the 

 dryer. 



THE DRYER. The "dryer " is a hollow iron cylinder 6 feet in diameter by 

 30 feet long, which revolves slowly; this motion causes the sugar to be continually 

 dropped on warmed pipes, which, with a current of hot air that is forced through 

 it, completely removes every vestige of moisture from the sugar ; the sugar passing 

 from the " dryer" goes over a screen which removes any lumps that may have 

 formed, and falls into a hopper from which it is sacked or barreled and is ready 

 for the market. 



The molasses that came from the "magma" is again boiled in the vacuum 

 strike pan, and another crop of sugar obtained from it, and also another lot of 

 molasses ; this second lot of molasses is too poor in sugar to be again crystallized 

 in the vacuum pan ; it is, however, concentrated to what is called " string proof" 

 in the vacuum pan, and dropped when finished into crystallizers, where it is con- 

 tinually agitated, which, with careful attention to temperature, causes all sugar 

 that can be obtained to crystallize. 



OLD METHODS. The usual custom (instead of recovering the last sugar by 

 means of crystallizers) is to deposit it in tanks, where, if remaining six months, 

 it would gradually crystallize ; but by the use of ' ' crystallizers ' ' the last sugar 

 can be obtained in four or five days. 



There is yet remaining a molasses too poor in sugar to be used except by sepa- 

 rate and expensive operations, the desirability of which depends on the price of 

 sugar recovered. 



The cheapest and most popular being the " Osmose " process : the molasses, 

 in suitable machines, is made to pass over a specially prepared parchment ; on the 

 other side is a current of hot water ; the salts that dissolve more readily than sugar 

 diffuse through this membrane to the water with which it is carried off; the 

 molasses which had been too impure to crystallize, now having become rid of some 

 of its impurities, will again crystallize ; this operation is carried on till there is 

 no molasses remaining. 



. The other is the " Substitution " process, and is based on the fact that finely 

 divided quick lime will, when in the presence of sugar, at a low temperature, 

 form an insoluble combination (sucrate of lime) ; this sucrate, when formed, is 

 recovered in filter-presses same as before described the impurities washed away 



