COPPER.
327
fluxes upon each other. The ore thus mixed is transported to the works m woodenmeasures that hold a hundred-weight. The workmen intrusted with the calcinationcornev the ore into the hoppers of the calcining furnace, whence it falls into the hearth;other workmen spread it uniformly on the surface by iron rakes. The charge of a fur-nace is from three tons to three tons and a half. Fire is applied and gradually increased,l ill> lowards the end of the operation, the temperature be as high as the ore can support■without melting or agglutinating. To prevent this running together, and to aid the ex-trication of the sulphur, the surfaces are renewed, by stirring up the ore at the end ofevery hour. The calcination is usually completed at the end of 12 hours, when the oreis tumbled into the arch under the sole of the furnace. Whenever the ore is cold enoughto be moved, it is taken out of the arch, and conveyed to the calcined heap.
The ore in this process hardly changes weight, having gained in oxydizement nearly•as much as it has lost in sulphur and arsenic; and if the roasting has been rightly man-ned, the ore is in a black powder, owing to the oxyde of iron present.
Second operation. Fusion of the calcined ore. —The calcined ore is likewise given tothe melters in measures containing a hundred weight. They loss it into hoppers, andit has fallen on the hearth, they spread it uniformly. They then let down thed°°r, and lute it tightly. In this fusion there are added about 2 cwt. of scoricc pro-ceding from the melting of the calcined matt, to be afterwards described. The objectthis addition is not only to extract the copper that these scoriae may contain, butspecially to increase the fusibility of the mixture. Sometimes also, when the composi-i lon of the ore requires it, lime, sand, or floor spar is added; and particularly the lastfluxmg article.
•The fnmace being charged, fire is applied, and llie sole care of the founder is to keep’P the heat so as to have a perfect fusion; the workman then opens the door, and“ Ils about the liquid mass to complete the separation of the metal (or rather of theatt) (Vo rn [p c scoria;, as well as to hinder the melted matter from sticking to the sole.e furnace being ready, that is, the fusion being perfect, the founder lakes out the°nte by the front door, by means of a rake. When the matt is thus freed from theWlf 1 ?’ a secon fl charge of calcined ore is then introduced to increase the metallic bath :ar lc 1 second fusion is executed like the first. In this way, new charges of roasted oreha* * n ** le matt ccfledefl on the hearth rises to a level with the door-way, whichflo^us commonly after the third charge. The tap hole is now opened; the mattand' 8, ° Ut: * n, ° l ' ie PA flflcfl with water, where it is granulated during its immersion;Vev 1 * c °Hects in the pan placed at the bottom. The granulated matt is next con-the lato l *' e matt warehouse. The oxydalion witli which the grains get covered bybe ,p Ct . 10n °A *bc water does not allow the proper color of the matt or coarse metal tog ra lsll uguished; but in the bits which stick in the gutter, it is seen to be of a steel*Pet a 'n- * ls fracture is compact, and its lustre metallic. The scorite often containsoir, e * C gl ains i they are broken and picked with care. All the portions which includeli aVe 'Metallic particles are re-melted in an accessory process. The rejected scoria;tin o.y en fl >l ' n( l to be composed of silicious matter 59, oxyde of copper 1, oxyde of
Platter* 1 * 8 ?P erat i°n, the copper is concentrated by the separation of a great part of thein gene 'V 1 ' 1 "’hich it was mixed or combined. The granulated matt produced, containsPiass i, ra ^ Per cent, of copper; it is therefore four times richer than the ore; and itspally eons equenlly diminished in that proportion. The constituent parts are princi-The nl^ ei ’. ' ron ’ an A sulphur.
tn.-e of th° St lni P orl ant point to hit in the fusion just described, is to make a fusible mix-s Pecifi c „ e earl ^ s and the oxydes, so that the matt of copper may, in virtue of its greateraUa ined'h aVl,y) ^ to the under-part, and separate exactly from the slag. This point is.
^hich 2^ 111611118 °f the metallic oxydes contained in the scorise of the fourth operation,°f iron. Were added to the charge. These consist almost entirely of black oxyde
height of ** le ores are vei T difficult to melt, a measure of about half a hundred-
but this must be done with precaution, for fear of in-
.... me
- of ftuor spar is added,leasing the sconce too much,^he business i
cou r . Se of S 94 ? eS 011 day and night. Five charges are commonly put through hands inthe ore j s f Us -\ | aours ! but when all circumstances are favorable—that is to say, whenc ° n dition ) evei s’ AV ^ en fuel is °f the first quality, and when the furnace is in goodThe charge 1 &1X c ^ ar ^ es a day have been despatched.
Ia rly to a calci ^ l °r anc * a °f ca l c i ne d ore, so that a melting furnace corresponds* nin £ furnace; the latter turning out nearly 7 tons of calcined ore in 24
Jearl
hours
Th,
Third ope m / 7 - are ^’ ( 1 by the ton.
Deration j s p r - , l * Calcination of the coarse metal , or the malt .—The object of thiscipaily to oxydize the iron, an oxydation easier to execute than in the first