shows the weight of the tailing, column 12 the percentage of lead, and column 13 the weight of lead contained in the tailing. From these latter analyses it is possible to again calculate the percentage of extraction of lead referred to the calcine leached, and also referred to the origial material, as shown in columns 14 and 15. The extractions calculated from the analyses of the solutions should agree with the extractions calculated from the analyses of the tailings and should furnish a check on the work. In practice, however, it is found that measurements on the solutions are less accurate than those on the tailing and the percentage of extraction calculated from the tailing analyses are the ones accepted as most reliable. The zinc tables (Nos. 50 and 56) and the copper tables (Nos. 51 and 57) are calculated in the same way as were the lead tables. Tables 52 and 58, containing the extraction summary, show the number of the roast, the number of the leach following the roast, and whether the leach was acid or neutral. The percentage of the total lead volatilized, the percentage of the total lead leached, and the sum of these two or the percentage extraction are shown. Similar data for zinc and copper are given. The lead, zinc, and copper tables contain the analyses and the weights of the various products, hence these data need not appear in the summary. TABLE 47. Data on roasting for tests of mixed flotation concentrate. NOTE.-Roasts 11, 12, and 13 were mixed in a laboratory ball mill with saturated brine, drained, and dried to about 10 per cent moisture content. |