M. TECHNOLOGY. 565 



SEPARATIXG BRASS FROM FOUNDERS' SLAG. 



All improved method of separating the brass from the 

 slaves of brass-founders consists in raixinor the substance with 

 limestone, coal dust, and oxide of iron, and subjecting the 

 whole to a melting heat. The brass settles at the bottom of 

 the melted slag, and can be drawn off in moulds. 6 C, y6'e/> 

 teiuber 19, 1872,378. 



REVIVIFICATION OF BONE-BLACK WITHOUT IGNITION. 



Bone-black used in the manufacture of sugar may be re- 

 stored to its original powers without the trouble and w^aste 

 of re-ignition as generally practiced. For this purpose a 

 two per cent, ammonia is employed, as suggested by Eis- 

 feldt. The bone-black is subjected to the usual fermenta- 

 tion, or boiling Avith caustic soda, and washing, and placed 

 on perforated bottoms in suitable iron vessels, and boiled 

 with ammonia, by aid of steam. The ammonia vapor given 

 off is condensed in worms, and used asrain. The boilins: lasts 

 about an hour, and is repeated, generally three times, until a 

 test portion of the ammonia, evaporated almost to dryness, 

 and heated with a few drops of caustic soda, does not turn 

 brown an indication that no more orQ:anic matter is dis- 

 solved by the ammonia. In avoiding the usual ignition, by 

 this process, there is not only economy of fuel, but of the 

 carbon of the bone-black, its active constituent, consumed 

 in ignition. Besides, no reduction of sulphate of lime to sul- 

 phide of calcium takes place, to be taken up by the sirup, 

 and produce dark-colored sulphides in contact with metals. 

 Most of the muriatic acid is also saved, and all of the soda, 

 in case of fermentation, at the cost of but little ammonia; 

 and, since the bone-black is not acted on by ammonia, the 

 waste is fifty to sixty per cent. less. The cost by this proc- 

 ess, on the whole, is only about two thirds of that by the old 

 one, while the purification may be made so thorough that the 

 filtration of the sirup is far better. 14 C, 1872, CCYL, 405. 



IMPROYEilENTS IN GLASS-SPINNING. 



Recent improvements in glass-spinning by Brunfaut, as set 

 forth in a communication of Professor Herrmann, j^romise to 

 develop a new branch of industry. Prolonged experiments 



