54 PHILIPPINE AGRICULTURAL REVIEW. 



ditions. Some operators apply it only at the centrifugals and 

 others apply it in the pan just at the graining point. Again 

 others use a quantity at both the pan and in the last charge of 

 water at the centrifugals. In any case, a good grade only of 

 the reagent should be used. This must be thoroughly dissolved 

 in clear water, condensed steam being preferred, and passed 

 through cloth or felt filters in order to remove any trace of lumps 

 which would tend to produce uneven bluing, or bluish streaks. 



While this is an excellent reagent in its place, it must not be 

 expected to whiten molasses sugars as was attempted by a local 

 manufacturer. 



Animal charcoal or boneblack. This material is made from 

 bones of animals, by burning them in a kiln built for that pur- 

 pose. The object of this burning is to remove the organic matter 

 and leave the remainder in a porous condition, so that it may be 

 crushed into particles the proper size. It is not desirable to 

 have a great amount of char dust present, since this retards 

 the passage of the liquors through the filters, as well as impair- 

 ing the efficiency of the work. 



Bone char, being very porous, absorbs a great volume of gases, 

 among which is oxygen, and it is ordinarily presumed that its 

 bleaching power may be attributed to this fact. Extensive ex- 

 periments have been made to determine definitely this point, 

 and the char has been subjected to an atmosphere of other gases 

 than oxygen. This proved that the char still contained great 

 clarifying power. 



Char also has a great surface attraction, which causes it to 

 collect particles of coloring matter that may be present, and thus 

 acts as an excellent filtering agent. New char should be 

 thoroughly washed with pure water until all the impurities are 

 removed. With the end in view of determining when the last 

 traces of chlorine have disappeared, chemical tests are made 

 on the wash waters. Nitric acid and silver nitrate are employed 

 for this purpose. After animal char has been used for some time 

 in the filters and fails to do its work efficiently, it is reburned, 

 or revived, as it is called. Ordinarily the best results are ob- 

 tained after a char has been used several times. 



Reburning of the char at too high a temperature should be 

 avoided, as it incurs an unnecessary loss of fuel, besides causing 

 serious injury to the char by a contraction of the pores. Since, 

 as stated previously, the main value of the char as a clarifying 

 and filtering medium lies in the fact of its porosity, anything 

 which reduces this will greatly impair its efficiency. One thing 

 in connection with the bone-char process of making white sugars 



