102 RTTLLETIN 42, UNITED STATES NATIONAL MUSEUM. 



As 80on as sufficient pig copper has accumulated to Iceep the refinery 

 running at least a mouth the refining furnace, which' is a rcverberatory, 

 similar to the roaster, is heated np, and the pig copper is charged into 

 it and melted. From 7,<iOO to 10,000 ])onnds are charged at a time and 

 about 8 hours are required to melt the charge. Wheu the charge is 

 thoroughly melted all slag that has accumulated is skimmed off. The 

 bath is then exposed to the air to remove the impurities by oxidation, 

 and as soon as sufficient slag has accumulated (generally in about 2 

 hours), it is skimmed. After this skimming the bath is "flapped," which 

 consists in striking the surface with a rabble, in order to throw the 

 uietal in thin sheets into the air, thus exposing a much greater surface 

 to oxidation. During the flapping samples of the bath are taken fre- 

 quently. The first samples have raised centers, but as the sulphur is 

 removed these become less and less, and finally, as the oxygen begins 

 to be absorbed in excess, the centre sinks, and when it sinks so far as 

 to crack on cooling, "crack set," the flapping is stopped. From 1 to 3 

 hours are consumed in flapping. Charcoal and wood are then thrown 

 on the bath and the lire nrged for 3 or 4 hours with the working door 

 closed. 



The bath is now skimmed, sawdust being thrown in to stiffen the 

 slag, and a sample taken. During the first flapping considerable cop- 

 per chills at the sides of the bath, which melts and runs down into the 

 bath when the door is closed. Should there be sufficient of this copper 

 to prevent the last sample from showing the crack set the bath must 

 be flapped again, but this is rarely necessary. 



Up to this point the bath has been subjected to violent oxidation to 

 remove the impurities, the most important of which is sulphur. The 

 total removal of the suli)hur can not be accomplished without intro- 

 ducing an excess of oxygen into the metal, which now has to be re- 

 moved by subje(;ting the bath to a reducing action. Pine charcoal is 

 thrown over the metal and an oak pole is introduced into the baih 

 through the working door ; this causes a violent boiling of the bath, 

 and the excess of oxygen introduced during the flapping is removed. 

 Samples are taken at short intervals, the centre of the sample gradu- 

 ally rises, and the surface becomes covered with fine wrinkles. As 

 soon as it shows a level set, a dark color, fine radiating wrinkles, con- 

 centric rings around the edge, and a thick rim without holes, the bath 

 is ready for ladling. 



The pole is now removed, the bath skimtned, and some fresh char- 

 coal thrown in to prevent oxidation of the copper. The metal is dipped 

 out in ladles and poured into copper molds. As soon as the surface 

 of the ingot is of the same color all over the mould is turned over and 

 the ingot falls into water. When cold they are removed and packed 

 into barrels. The black copper yields about 80 per cent, of ingot, and 

 ingots weigh from 13^ to 14 poiinds. 



