514 



METALS. 



The green flux is formed of three distinct 

 parts : glass, or the dissolving agent, to which 

 lime may be added ; fluor-spar, or the fluidify- 

 ing agent; and protoxide of manganese and 

 liine also, or the refining agents. The author 

 says : 



Any kind of oil is good enough for the purpose. 

 The mixture must be made (shortly before introdu- 

 cing into the crucible ; for, if it is left standing for 

 some hours, especially in an open vessel, it is apt to 

 catch fire, and is then unfitted for smelting. Should 

 this occur, the addition to the burnt mixture of about 

 45 parts of lamp-black or soot and some more oil 

 would remedy the accident. But it is only after 

 standing some eight hours that the mixture takes 

 fire. The mixture is introduced into the crucible and 

 slightly pressed in, and a round cover of thick wood 

 is placed over it. It is carbonized during the smelt- 

 ing, and forms a charcoal cover which protects ad- 

 mirably the mixture from oxidation, and it can bo 

 used several times. The clay or plumbago cover is 

 then placed over the crucible, and the joint is luted 

 with a little thin fire-clay. A small aperture is kept 

 to allow the gases to escape. The crucible is then 

 placed in a wind or blast furnace, and slowly heated 

 so long as fumes escape from the crucible. The heat 

 is then rapidly increased until it reaches white heat, 

 and the furnace is maintained at that high tempera- 

 ture for several hours, the time required depending, 

 of course, on the quantities operated upon. When 

 it is thought that the operation is done, the fire is 

 allowed to burn away and the crucible is left to cool. 

 The cover is then removed by means of a chisel in- 

 troduced in the joint. The crucible is turned upside 

 down, and shaken until the slag and metal fall down. 

 The button of metal is detached from its slag with a 

 hammer, and introduced in well-corked or stoppered 

 vessels, perfectly dried. The slag, which has a fine 

 olive-green color, breaks up in fragments with large 

 faces affecting a pseudo-crystalline structure, but the 

 grain is really crystalline. It is ground and used as 

 flux in a second smelting. It is advisable after each 

 smelting to add to the slag, in order to make it more 

 fusible, about TO of the white flux. The mixing 

 of manganese ore, flux, and. lamp-black is not an in- 

 different operation, and to insure perfect success it 

 should be done in the following way : The oxide of 

 manganese should be first of all thoroughly mixed 

 with the lamp-black. Then this mixture should be 

 pretty roughly mixed with the flux, and then oil 

 should be added. By so doing, lamp-black and ox- 

 ide of manganese remain united during the mixing, 

 and act upon each other during the smelting, before 

 the flux begins to melt, so that the oxide is reduced 

 to the metallic state before the flux can dissolve any 

 portion of it. The residue of carbon left by the burnt 

 oil assists in reducing the oxide of manganese, and 

 in preventing the flux from acting upon it before it 

 has been reduced to the metallic state. 



The Manufacture of Malleable Iron. The 

 Mechanics* Magazine for November contains a 

 paper by Mr. K. W. Davenport, on the results 

 of a chemical investigation on some points in 

 the manufacture of malleable iron. His ob- 

 ject was, to ascertain the precise effects of the 

 annealing process, and he made analyses of 

 samples botli before and after annealing. The 

 iron used was a fairly good charcoal-iron. The 

 unannealed castings, when broken, showed a 

 white fracture, all the carbon being in the 

 combined state ; a property essential to secure 

 the success of the annealing process. Mr. Da- 

 venport's principal conclusions are thus given: 



First, that the silicon, phosphorus, and manganese 

 are in no way affected by the annealing process ; sec- 



ond, that the amount of sulphur is not diminished, 

 and may be slightly increased; and third, that the 

 amount of carbon is reduced by each annealing, until 

 finally a mere trace remains. The slight increase of 

 sulphur shown by both sets of analyses is probably 

 due to the presence of that substance in the coal used 

 for fuel. The castings before annealing, containing 

 3i per cent, of combined carbon, showed, on break- 

 ing, a white fracture, and were too hard to be cut by 

 a drill ; after the first annealing an interesting change 

 showed itself in the fracture ; a whitish surface ex- 

 tended in about TO of an inch on all sides, sur- 

 rounding a dark core of dull-black color ; the line of 

 change from the light to the dark was quite distinct, 

 and the whole was easily cut by a drill. A portion 

 of this white outside layer was filed off, and the car- 

 bon determined to be present only in traces, while 

 analyses show the presence of a considerable amount 

 of carbon, when a sample of the entire cross-section 

 was taken. After the second annealing the black 

 core had entirely disappeared, the whole fracture 

 being of the same appearance as the white border. 

 The amount of carbon in a sample of the whole cross- 

 section, as shown by the analysis, was reduced to a 

 trace. It would appear from the above that, when & 

 casting does not much exceed i of an inch in thick- 



ination only extends from the surface into the mass 

 for a certain distance, but may be carried farther in 

 by a repetition of the process. It would also seem 

 that in the interior of a thick casting, where the 

 amount of carbon is at all events only partially re- 

 duced, that which remains is, by the ^high heat and 

 subsequent slow cooling, changed in its state of oc- 

 currence from combined carbon to a species of un- 

 combined or graphitic carbon ; for, where the iron 

 before annealing is white and very hard, after an- 

 nealing it shows a dark fracture and is quite soft. 

 Its behavior, too, with nitric acid would lead to the 

 same conclusion, for while the white, unannealed 

 iron dissolved perfectly in that reagent, ^upou stand- 

 ing a few hours, and gave to the solution the same 

 clear brown color that is noticed when a high steel 

 is so treated, the annealed black heart, as it is tech- 

 nically called, gave a dirty-green color to the solu- 

 tion, and a black; carbonaceous residue remained. 



The manufacturers of malleable iron are occasion- 

 ally troubled by a lack of toughness in the annealed 

 castings when these are exposed to a sudden blow 

 or to a bending strain. This weakness is at times, 

 doubtless, caused by the natural rottenness of the 

 iron, owing to the presence of an excessive amount 

 of silicon, phosphorus, or sulphur; but it also must 

 frequently be due to a crystalline structure which the 

 iron, under certain unknown conditions, assumes 

 while being annealed. This structure shows itself 

 in the fracture of an annealed casting in the form of 

 bright crystalline faces, which occasionally extend 

 entirely across the fracture. 



Pure Wrought - Iron. By the Henderson 

 process, according to the London Chemical 

 News, pure wrought-iron has been made on 

 the commercial scale, at the Bowling Works, 

 Bradford. The analysis of the pig-iron used 

 was: 



Per cent. 



Graphitic carhon 3.155 



Combined carbon 0.581 



Silicon 1.646 



Sulphur 0.070 



Phosphorus 0.685 



Manganese 1-472 



Iron.. ^92.644 



Total 100.203 



The wrought-iron from the above analyses: 



