mat

Also called matte (kawa). An intermediate product formed when several sulfides melt in a furnace during metal smelting. It is extremely important in the smelting of Cu and Ni, and usually contains mainly Cu ₂ S, Ni ₃ S ₂ , and FeS, with small amounts of PbS, ZnS, Au, and Ag. In the case of Cu smelting, it can be thought of as a binary system of Cu ₂ S-FeS, and in the case of Ni smelting, Ni ₃ S ₂ -FeS. When this matte melt is placed in another furnace and subjected to oxidation refining, metallic copper is obtained by the following reaction:

2Cu(l) + FeO(into slag) + _2SO2 (g)

The reason why matte is produced in copper smelting is that the ore is a sulfide and contains only a few mass percent of Cu, so by producing matte in a high-temperature furnace, Cu can be extracted very efficiently from the ore. As mentioned above, Au and Ag are concentrated in the matte as impurities, so Au and Ag are produced as by-products in the smelting of Cu and Ni.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

鈹(かわ)ともいう．金属製錬においていくつかの硫化物が炉中で溶け合って生成する中間産物．Cu，Ni製錬ではきわめて重要なもので，普通，Cu₂S，Ni₃S₂，FeSが主体でそのほかに少量のPbS，ZnSやAu，Agも含有する．Cu製錬の場合はCu₂S-FeS，Ni製錬の場合はNi₃S₂-FeSの二元系と考えてよい．このマット融体を別の炉に入れ酸化精錬を行うと，次の反応で金属銅が得られる．

2Cu(l)＋FeO(スラグ中へ) ＋ 2SO₂(g)　　

銅の製錬においてわざわざマットをつくる理由は，鉱石が硫化物で，かつそのCuの含有量が数質量％ くらいであるので，高温炉に入れマットをつくると非常に効率よくCuを鉱石から抽出できるからである．前述のようにマットのなかには不純物としてAu，Agが濃縮するので，CuやNi製錬の副産物としてAuやAgが生産される．

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