The stove is of the usual [shape: alternating up-down pipe] cast-iron pipe form, designed to give the maximum exposing surface, suitably strengthened and protected from direct action of the fire. Much valuable information on the advantages, disadvantages, and appliances for blast heating was afforded by the smeltermen who contributed to the symposium on “Pyrite Smelting,” which Rickard edited for the _Engineering and Mining Journal_. References. Mathewson, E. P., “The Development of the Modern Blast Furnace.” _Eng. and Min. Journ._, May 27, 1911, p. 1057. Wright, Lewis T., “Metal Losses in Copper Slags.” _Bulletin Amer. Inst. Min. Eng._, 1909, Sept., No. 33, p. 817. Shelby, Geo. F., “Cananea Blast Furnaces.” _Engineering and Mining Journal_, April 25th, 1908. Emmons, N. H., “Copper Blast-Furnace Tops.” _Bulletin Amer. Inst. Min. Eng._, Feb., 1911, p. 119. “Heating Blast.” _Engineering and Mining Journal_, June 16 and Sept. 15 and 29, 1906. “Pyrite Smelting,” T. A. Rickard. Also the Authors already referred to, Austin (p. 80), Gowland (p. 17), Peters (p. 80). LECTURE VII. =MODERN BLAST-FURNACE PRACTICE= (_Continued_). Charge Calculations — Charging — Working — Disposal of Products — Pyritic Smelting — Sulphuric Acid Manufacture from Smelter Gases. =Charge Calculations.=—Modern practice aims at the production of a matte of converter grade, containing usually from 40 to 50 per cent. of copper, and preferably in a single smelting operation; except in true pyritic work.[12] Full analysis of the whole supply of material available at the smelter is essential, as well as a report on the quantities of each separate constituent. The first step in the charge-calculation is the computation of the total weights of copper, iron, and sulphur available for the smelting campaign; from these quantities the losses of copper and sulphur to be allowed for during the operation itself, as based on previous experience, are deducted. The balance indicates the quantities of these elements from which the matte and slag can be produced. The copper is transformed into matte, in which product it may be regarded as existing in the form of copper sulphide, Cu_{2}S, and the sulphur required for this combination with the copper is calculated from the relation— Cu_{2}S = Cu_{2} : S :: 2 × 63·5 : 32 :: 127 : 32 :: 4 : 1 approximately. Thus every unit of copper combines with one-quarter of its own weight of sulphur. A matte of converter grade containing, say, 44 per cent. of copper is constituted as follows:—Copper, 44 per cent. + sulphur, 11 per cent., or copper sulphide, 55 per cent., the remaining portion of the matte being iron sulphide, which amounts to 100 − 55, or 45 per cent.