2.04 pm Sample No. 13 blowing, │ 2 │ 10 │ 0·052│ 0·01│ 0·78│0·033 2.05 pm Punched 2 minutes. │ │ │ │ │ │ 2.08 pm Blow stopped, test for Cu.│ │ │ │ │ │ 2.09 pm Blow resumed. │ │ │ │ │ │ 2.10 pm Blow finished. │ │ │ │ │ │ Converted copper, │ 2 │ 16 │ 0·017│trace│ 0·01│0·033 Total time punching, │.. │ 28 │ .. │ .. │ .. │ .. Total time of blow, │ 2 │ 16 │ .. │ .. │ .. │ .. Actual time of blow, │ 2 │ 09 │ .. │ .. │ .. │ .. ───────────────────────────────────┴───┴────┴──────┴─────┴─────┴───── Samples taken each 10 minutes from beginning of blow until finished. In general character, this colour sequence, during the bessemerising of the ordinary class of copper mattes—_i.e._, those consisting largely of iron, copper, and sulphur, with but moderate quantities of impurity—does not vary very markedly, but the body and luminosity of the flame depend to a great extent on the nature of the charge and on the working conditions. The colours are intensified by very hot metal, large charges, heavy blast, and rapid working, and particularly by the presence of secondary constituents, such as zinc, lead, or arsenic, which liberate dense white fumes, and so increase the luminosity of the flame. There are generally four main variations in the appearance of the flame from the acid-lined converter:— ┌─ ─┐ │Oxidation of secondary │ Dark reddish-brown At commencement ─┤ constituents, ├─ flame. of blow, │Burning of iron, sulphur,│ Accompanied by much └─ and coal, ─┘ smoke. Slagging stage, Iron-sulphide oxidation, Apple-green flame. White metal stage, Copper oxidation in White-blue flame. presence of slag, Blowing to blister Sulphur oxidation, Thin red-purple flame. copper, The changes in composition of the charge during a converter blow have been traced by Mathewson, who assayed samples during the various stages; some of these results are indicated in Table xii. and in Fig. 66. For full record see _Trans. Amer. Inst. Min. Engineers_, 1907. In general, of the constituents present in the matte, iron and sulphur are removed very readily, 96 per cent. of the former and 53 per cent. of the latter in the slagging stage of the blow, whilst the elimination of the injurious impurities is high, bismuth and arsenic being removed to the extent of upwards of 90 per cent., and of the antimony, selenium, and tellurium, from 40 to 70 per cent. are eliminated (see p. 217).