DEFECATION WITH LEME. 295 



juice, is to avoid the mixing up of the scum in the juice, as it is 

 now in a condition to be completely removed with almost no loss of 

 juice. 



Many experiments have been made (as will be seen by reference to 

 page 316) for the purpose of learning at what temperature the lime 

 should be added ; and there appears to be no difference whether the 

 lime is added to the jiuce at the ordinary temperature, or at anv TX)int 

 under boiling. Owing to the possibility that the acids of the juice mav 

 cause the inversion of some of the sugar after the heating is begun, 

 also in order to have ample time for adding the proper amount of lime 

 before the boiling point is reached, it would seem to be desirable to add 

 the lime as soon as possible after turning on the heat. 



If an excess of lime is used, it will result in giving a darker color to 

 the juice and to the syrup produced from it. 



After having withdrawn the heat, the contents of the defecator are 

 left at rest for from fifteen to twenty minutes, after which the scum 

 may be carefully removed by a large skimmer, pierced with holes not 

 over one-sixteenth of an inch in diameter ; and this scum may be 

 emptied into a gutter, upon one side of the defecator, by which it may 

 run to the scum tank foi future treatment. 



The disposition of the skimmings will be discussed in the chapter on 

 waste proilucts, page 376. It will be found possible to remove almost 

 every particle of scum in this manner, with but little loss of juice. 



It is, with many, the practice to fill the defecator with the fresh 

 juice, and then, after liming, bring it to the boiling point, and letting 

 it boil gently, to sweep off the dense scum into a gutter attached to one 

 side of the defecator, which is about four inches lower than the other 

 three, so that whatever boils over shall be s:ived with the scum. This 

 method is very wasteful, unless the scum is treated by filters to recover 

 the juice lost, and is uneconomical, since it necessitates the filtering of 

 very much more juice. It is a practice, in short, having nothing to 

 commend it. 



After skimming the contents of the defecator, it will be found, when 

 the juice has fallen to a temperature of about 85°C. (185°F.), that the 

 sediment has quite subsided, and occupies a depth of about two inches, 

 the defecated juice above being perfectly clear and almost colorless, 

 resembling a very pale sherry. 



Such a result may be regarded as an indication of a successful defe- 

 cation. Too little lime will be indicated by a turbid, cloudy liquor ; 

 and too much lime by a bright, clear juice, but darker color. 



For the purpose of watching the pr^^'gress of the precipitation of the 

 sediment, and to learn when it is completed, it is convenient to have 



