At commencement of blow, |  | Oxidation of secondary constituents, |  | Dark reddish-brown flame. |
| Burning of iron, sulphur, and coal, | Accompanied by much smoke. | |||
| Slagging stage, | Iron-sulphide oxidation, | Apple-green flame. | ||
| White metal stage, | Copper oxidation in presence of slag, | White-blue flame. | ||
| Blowing to blister copper, | Sulphur oxidation, | Thin red-purple flame. | ||
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]).
Working of a Typical Charge in Silica-lined Converter.—The Anaconda converter plant is now being operated with basic linings. The former practice at this works was representative of the best type of acid-lined working, and the following description, based upon this practice, is typical of the method in general use. There were in operation twelve converter stands of the dimensions previously given. Normal working was to convert the 45 per cent. copper matte to white metal, to pour off slag, blow to blister copper, and pour the resulting metal—in regular sequence.
The colour-changes in the flame during bessemerising are indicated in the colour-photographs reproduced in the frontispiece.
Fig. 66.—Composition of a Charge during Bessemerising Operation.