HOW TO REVIVIFY BONEBLACK. 145 
pillar, or right rectangular prism, closed at the top by a 
movable iron plate, and below by a double trap door, open- 
ing downward. Surrounding this retort is a furnace of 
brick work, of the same height as the retort, but wider 
below than above. (Pereira.) 
The revivification of the boneblack used in this process 
may perhaps most readily be accomplished by inclosing it 
in a cast-iron cylinder, placed horizontally in the floor of 
the evaporator furnace itself, just beyond the grate bars. 
The cylinder may be revolved, so as to expose its contents 
equally to the heat, by means of projections at its ends, 
outside of the furnace walls, where also there are openings 
through which to fill and empty the retort. 
A method of restoring, or even of augmenting (as is 
asserted), the powers of animal charcoal has recently been 
discovered by Mr. Edward Beanes, of England, who intro- 
duced some improvements in sugar manufacture in the 
Island of Cuba. It consists* in treating the exhausted 
charcoal, when dry and hot, with dry hydrochloric acid 
gas, which it absorbs with astonishing avidity. Another 
portion of charcoal is then added to that which has received 
the acid gas, the combined gas remaining in the pores of 
the latter is taken up by the former, and the whole becomes 
neutral: chloride of calcium is formed, which is easily 
washed out, and the charcoal is then reburned in the usual 
way. ‘The advantages of this method are said to consist 
chiefly in the removal of any lime that the charcoal may 
have taken up without attacking the phosphate, and in 
augmenting the decolorizing powers of the coal more than 
100 per cent. The efficiency of this means has not yet 
been tested in this country. 
Freshly burned charcoal should be carefully excluded 
* Medlock, in London Chem. News—Sci. American, vol. xiii. p. 224. 
15 
