62 



BONE-BLACK. 



loan to each of the republics of $3,000,000, 

 making $6,000,000, for the privilege of work- 

 ing the deposits under a triple partnership, viz. : 

 Chili, Bolivia, and the French firm, each taking 

 a fair share of the profits. By this course of 

 action a war was prevented between the two 

 nations ; a large loan was given to each ; unity 

 of feeling was engendered, and the danger of 

 foreign interference prevented. 



BONE-BLACK, REVIVIFICATION or. Mr. II. 

 Medlock, treating of this subject in a brief but 

 very satisfactory article in the Chemical News, 

 of February 17, 1865, notes the fact that the 

 principal source of expense in a sugar refinery 

 (see SUGAR, MANUFACTURE OF, etc.) is that of the 

 animal charcoal; so that, to the refiner com- 

 mencing with new black [some loss continually 

 being of course involved, still] it is a great de- 

 sideratum to have the means of keeping the bulk 

 of the material in a condition of unimpaired de- 

 colorizing power. 



In bone, the phosphate of lime forms a struc- 

 ture showing innumerable and almost micro- 

 scopic cells; while the gelatine enters these, and 

 binds the whole also into one mass. Of the 

 whole, the gelatine constitutes about .310, the 

 phosphate of lime .631, and the other salts .059 

 parts. In charring (distilling) the bone, the 

 gelatine is decomposed, giving off volatile mat- 

 ters, leaving the bone finely porous, and each 

 cell and pore lined with particles of minutely- 

 divided carbon. Although the specific physical 

 or chemical principle involved in the decolor- 

 izing and purifying of syrups and like liquids by 

 bone-black is not yet clearly understood, it is, 

 at least, known that the admirable fitness of the 

 black for the refiner's use is to be explained by 

 the fact of its detaining and withdrawing from 

 the syrups, up to the point at which its capacity 

 in this respect becomes saturated, both the ma- 

 terials which impart color, odor, or fermenting 

 tendency, and also various metallic oxides and 

 salts which such liquids contain. 



When, from such absorption, the purifying 

 capacity becomes saturated, and lost, the cause 

 is commonly assumed to be that the carbon par- 

 ticles have become coated over with the albu- 

 minous and other gummy matters of the solu- 

 tion, and the porosity of the black thus impaired. 

 Mr. Medlock admits this to be one cause ; but, 

 as has recently been urged by Leplay and others, 

 he, too, regards as the principal cause the ac- 

 cumulation in the pores of lime (and of course 

 its carbonate also) from the sugar solution. 

 This view is supported by the facts that the 

 mere repeated reburning of the bone-black, al- 

 though this must remove all organic matters the 

 latter has retained, does not completely restore 

 its purifying power ; and that, under such treat- 

 ment alone, any bone-black eventually becomes 

 worthless. Corenwinder, an eminent German 

 chemist, has stated as axiomatic the principle 

 that, "The decolorizing power of charcoal in 

 sugar-refining is correlative to its power of ab- 

 sorbing lime." And it has been calculated that 

 the lime the remains of that used in treating 



the cane-juice already in the raw sugars re- 

 fined in England, amounts to from Y to 10 Iba. 

 to the ton. 



The modes that may separately be resorted 

 to for restoring the power of bone-black, are 

 those of 1, washing it with hot water; 2, 

 charging with water and leaving several days 

 to ferment ; 3, washing with very dilute chlor- 

 hydric acid ; 4, exposing to the slow action of 

 air and moisture ; 5, reburning, that is, heating 

 in closed retorts, to redness. Commonly two 

 of these modes are combined, as, by washing 

 with water and then reburning ; or, fermenting, 

 drawing off the liquid, and then replacing it 

 with fresh, acidulated with to -J- per cent, of 

 chlorhydric acid. This, and a little acetic acid 

 formed during fermentation, dissolve out some 

 of the retained lime ; but they also attack the 

 lime-salts of the bone, rendering the latter fria- 

 ble and causing waste. 



Ure (Supplement) describes four modes of 

 reburning bone-black; namely, 1, the common' 

 method of burning in iron pipes, in which, how- 

 ever, the black is liable to be unequally acted on, 

 and the pipes to be destroyed by corrosion ; 2, 

 that of Parker, improved by Chantrell, of burn- 

 ing in fire-clay chambers, not liable to be cor- 

 roded, and which is now coming into more 

 general use; 3, Mr. Torr's method of burning 

 in rotating cylinders; and, 4, that of MM. 

 Laurens and Thomas, of reburning in a proper 

 apparatus by superheated steam. The latter 

 two, though expensive, both give excellent re- 

 sults. The authority just quoted also remarks : 

 " To reburn charcoal, the best methods are 

 those which most rapidly remove the water, 

 raise the temperature of each grain of charcoal 

 to a uniform temperature (sic) of 700 F., and 

 which admit of its being readily cooled without 

 contact with the air." 



Some years since it was a quite general prac- 

 tice to use the same black (wastage excepted) 

 for a period of six months, more or less, return- 

 ing every day the portions used on the pre- 

 ceding, or, as often as the decolorizing power 

 failed. At the end of such period, the charcoal 

 was laid aside as no longer available ; and lat- 

 terly, it has then commonly been employed for 

 the making of "superphosphate of lime," for 

 fertilizing. The plan now resorted to by many 

 refiners, is that of washing the black, as it comes 

 from the filters, with water, then reburning, 

 sifting out occasionally such fine dust as will to 

 some extent necessarily result, and as the water 

 may not have removed, and then returning 

 again into the filters; varying this course, how- 

 ever, as often as may be judged necessary, with 

 a view to freeing the black more effectually of 

 lime, by removing the contents of the filters 

 after use directly into "fermentation tanks," 

 adding water acidulated with a little (about one- 

 half of one per cent.) chlorhydric acid, and al- 

 lowing to ferment for seven days ; then drawing 

 out and washing, in order to remove the chloride 

 of calcium which has resulted from action of 

 the acid on the absorbed lime ; when, finally 



