2d.)+(8-3/4?(3s. 9d.)), or ?2 5s.
If, for example, Chili bars, containing 96 per cent. of copper, bring
?50 per ton, the standard is ?71 9s. 4d. It is got at in this way.
The returning charge on a 96 per cent. ore is (12s. 2d.)+(96?(3s.
9d.)), or ?18 12s. 2d. This added to ?50 gives ?68 12s. 2d.,
and this multiplied by 100 and divided by 96 (100 tons of the bars will
contain 96 tons of fine copper) will give ?71 9s. 4d.
The price of 100 tons of pyrites, containing 2-1/4 per cent. of copper
by dry assay, would be got on this standard as follows:--The parcel of
ore would contain 2-1/4 tons of copper. This multiplied by the standard
gives ?160 16s. 0d. From this must be deducted the returning charge,
which for 1 ton of ore of this produce would be (12s. 2d.) + (2-1/4?(3s.
9d.)) or ?1 0s. 7d., and on the 100 tons is ?102 18s. 4d. This would
leave ?57 17s. 10d. as the price of the parcel, or 11s. 7d. per ton.
This would be on the standard returning charge of 45s. (for 8-3/4 per
cent. ore); if a smaller returning charge was agreed on, say 38s., the
difference in this case, 7s., would be added to the price per ton.
WET METHODS.
The solubility of the ores of copper in acid has already been described,
but certain furnace products, such as slags, are best opened up by
fusion with fusion mixture and a little nitre.
Pages:
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350