1 gramme there is 2 to
3 grammes of the oxalate present. The hot solution is then directly
submitted to the action of the electric current. After the iron has been
precipitated, it is best to stop the action of the current before all
the aluminum oxide is thrown down, for otherwise a portion of the latter
may adhere firmly to the iron, and be difficult to remove.
In such a case, as was mentioned previously in the separation of iron
from manganese, it is necessary to redissolve the iron (after previously
having poured off the liquid) in oxalic acid, and then the electrolysis
is continued.
In order to effect the complete precipitation of the aluminum oxide from
the solution which was poured from the iron, ammonium hydrate is added,
and the solution boiled for some time, and then the aluminum oxide is
determined in the usual manner. When the quantity of aluminum is less
than that of iron, this method may be relied upon to give exact results.
With the reverse (_i. e._, an excess of iron) the precipitate
of aluminum oxide must be dissolved in oxalic acid (without the
interruption of the current), and the electrolysis continued.--_Berichte
der Deutschen Chemischen Gesellschaft_, 14, 1662.
* * * * *
THE CULTIVATION OF PYRETHRUM AND MANUFACTURE OF THE POWDER.
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