The assay resolves itself
into one for the determination of ferrous iron, for which the standard
solutions and method of working described under _Iron_ are used.
The assay is as follows:--For rich ores, 2 grams of clean soft iron wire
are treated, in a pint flask, with 100 c.c. of dilute sulphuric acid and
warmed till dissolved. Carefully sample the ore, and in one portion
determine the "moisture at 100° C.;" grind the rest in a Wedgwood mortar
with a little pure alcohol until free from grit. This reduces the
substance to a finely-divided state and assists solution. Evaporate off
the alcohol and dry at 100° C., mix well, and keep in a weighing-bottle.
Weigh up 2 grams and add them to the solution of iron in the flask;
carefully wash it all down into the acid liquid. On rotating the flask
the ore will rapidly dissolve, but gentle heat may be used towards the
end to complete the solution. When the residue is clean and
sandy-looking, and free from black particles, the flask is cooled, and
the residual ferrous iron is determined by titration with
"permanganate." The iron thus found, deducted from the 2 grams taken,
will give the amount of iron peroxidised by the dioxide contained in the
2 grams of ore. This divided by 2 and multiplied by 77.68 will give the
percentage of dioxide in the sample, or multiplied by 49.
Pages:
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564