c. of hydrochloric
acid. Evaporate to a paste, add 5 c.c. of the sodic acetate and acetic
acid solution, dilute to 100 c.c. with water, boil, and titrate with
uranium acetate solution.
In an example, 0.5 gram of apatite required 37.4 c.c. of uranium acetate
solution (standard equal to 0.5291 gram of phosphoric oxide). The sample
therefore contained 0.1979 gram of P_{2}O_{5}, equal to 39.58 per cent.
~Determination of Phosphoric Oxide in an Iron Ore.~--Take 10 grams, boil
with 50 c.c. of hydrochloric acid, and evaporate to a paste; take up
with 10 c.c. of dilute hydrochloric acid, and dilute with water to 400
c.c. Pass sulphuretted hydrogen for nearly a quarter of an hour; warm,
and filter. Boil off the excess of gas; cool, add ammonia till nearly
neutral, and then a few drops of ferric chloride solution, and 4 or 5
grams of sodium acetate, with a drop or two of acetic acid. Boil and
filter. Dissolve the precipitate in hot dilute hydrochloric acid, and
add citro-magnesia mixture and ammonia; allow to stand overnight;
filter, ignite, and weigh.
In an example, 10 grams of ore gave 28.5 milligrams of magnesic
pyrophosphate, which is equivalent to 0.18 per cent. of phosphoric
oxide.
~Determination of Phosphorus in Iron.~--Take from 2 to 10 grams
(according to the amount of phosphorus present), and dissolve in aqua
regia, keeping the nitric acid in excess; evaporate to dryness and take
up with hydrochloric acid, boil, dilute, and filter.
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