c. of
sodium acetate and acetic acid solution; transfer to a pint flask, boil,
and titrate.
For example, an impure sample of ore required, in duplicate assay of
half a gram each, when treated in the above-mentioned way, 39.6 and 39.5
c.c. of the uranium acetate solution (100 c.c. = 0.537 gram of arsenic),
equivalent to 0.2114 gram of arsenic, or 42.3 per cent.
An alternative method is as follows. Powder the ore very finely and
weigh up .5 gram. Place in a 2-3/4 inch berlin dish and add strong
nitric acid, one drop at a time until the action ceases; with care there
need be no very violent reaction. Dry over a water bath. Cover with 2
grams of nitre and over this spread 5 grams of a mixture of equal parts
of nitre and carbonate of soda. Fuse in a muffle or over a large gentle
blow-pipe flame for 4 or 5 minutes. This will spoil the dish. Allow to
cool and boil out in a larger dish with 100 c.c. of water. Filter and
wash into an 8 oz. flask. Acidify the liquor with nitric and boil down
to about 100 c.c. The acid should not be in too large excess, but an
excess is needed to destroy nitrites. Neutralise with soda or ammonia.
Add 5 c.c. of the mixture of sodium acetate and acetic acid. Titrate
with uranium acetate.
~Determination of Arsenic (As) in Crude Arsenic.~--The method given
under the iodine titration simply determines that portion of the arsenic
which is present in the substance as arsenious oxide or white arsenic.
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