350 SORGHUM. 



case it will not run from pan without steam pressure from within), 

 many boiling it so closely that in two minutes more it would be liable 

 to set. 



For the economical working of a pan, a recipient is furnished. It 

 has many nozzles, so as to connect the exhaust from the various en- 

 gines iu the sugar house, and is connected to the steam trunk with 

 suitable openings, and these in turn connected to the valves on pan 

 by copper pipes. To guard against too much back joressure, the re- 

 cipient has an escape valve, loaded to a working pressure of about five 

 pounds ; and also so arranged that, when the pan is not working, the 

 steam can escape perfectly free. 



The recipient also has a water guage and outlet cock. 



The condensation of the eliminated vapors of the juice during the 

 boiling, is accomplished in a condenser that is connected to the vacuuni 

 pan tor the purpose of producing this effect by the injection of cold 

 water, which, coming in contact with these vapors, produces the 

 vacuum desired. 



This condensation and injection water is drawn off by means of a 

 large air pump, which, at the same tifne, takes out any air which may 

 have been admitted through any leaks in the machinery, together with 

 the air which we know to be in the water. 



Without sufficient cold water, it is impossible to procure a perfect 

 condensation and a proper vacuum ; and, where this occurs, it is impos- 

 sible to do the work required of the pan. 



From 24 to 29 inches of vacuum are considered necessary; and if 

 this is not shown by the mercury gauges, some imperfection exists 

 which ought to be remedied at once. 



The operation of boiling is as follows: The juice is elevated into 

 the tanks above by means of a steam pump, fi'om whence the pan 

 draws it. After cooking a strike, which operation lasts from four to 

 six hours, it is thrown out by means of a valve at the bottom of the 

 pan into a mixer (see illustration), which is sufficiently large to con- 

 tain the entire strike of the pan. Afterward, the sugar passes from 

 the mixer to the centrifugals through a valve opening into each of the 

 machines, where it is purged, ready to be emptied into either boxes or 

 hogsheads, and sent to market. This system is called purging " hot," 

 and is used to-day in all the refineries of the United States and on 

 many jilantations. For raw sugar, the vacuum pan can be made to 

 operate on the " wet " or " dry " system. The latter, Avhich is the most 

 modern, is preferred by all who thoroughly understand the matter, but 

 it requires more water. A plantation having complete machinery will 

 make six thousand barrels of sugar with greater ease and less labor 



