A N T I M O N Y : ITS HISTORY, CHEMISTRY, MINERALOGY ...

THE ANALYSIS OF ANTIMONY COMPOUNDS. 185
tartario acid or potassium bitartrate, which are without action on
iodic acid.
(8) Joseph Hanns,* in Ckemilcer Zeitung, 1897, proposes to determine
antimony volumetrically by precipitating it as sulphide, filtering
and washing the precipitate with water; the precipitate is washed
into a beaker and ferric sulphate added (either in powder or in
solution) in the proportion of 6 parts to 1 part of antimony
sulphide. The solution is then boiled for fifteen minutes. The
reaction is:—
Sb2S8 + 5Fe2(SO4)3+5H2O = H2Sb205 + 10FeSO4 + 5H2SO< + 33.
The contents of the beaker are then diluted considerably, and 15 c.c.
of concentrated sulphuric acid are added for each gramme of ferric
sulphate used. The solution is then cooled quickly to 25° C, and
titrated to a faint rose colour with potassium permanganate. The
permanganate solution is made up to a strength of 1 to 1 *5 grammes
per litre and is standardised against antimony trioxide. The amount
of antimony sulphide in the precipitate treated with the ferric sulphate
should not exceed 0*2 to 0*3 gramme.
(e) Dv Clark, * in Journ. 8oc. Chem. Ind., 1896, recommends for
antimony ores and alloys a modification of Mohr's method t of titration
with y^ solution of iodine :—
av If the ore is free from arsenic and iron, dissolve in HOI, drive
oft H2S by heat, add tartaric acid or Rochelle salt, make alkaline
with^NaHCOg, and titrate.
Pv If iron is present, dissolve in HC1, precipitate with H2S, redissolve
in HC1, and proceed as before.
yr If arsenic is present, dissolve in HC1 +- Fe2Cl6 and distil off the
arsenic; precipitate Sb with H2S, and proceed as under j8r The
arsenic distilled off may be condensed and estimated by titration
with YQ solution of iodine.
8r When the ore or alloy contains tin, dissolve in HC1 + Fe2Cl6,
distil off As, precipitate Sb with metallic iron, redissolve, after
washing in HC1 plus a little KC1O3, filter off the insoluble impurities
derived from the iron, precipitate Sb with H2S, and proceed as
under yr
According to Mr L. Parry, the most accurate and practical methods
are, titration of Sb2O3 with iodine in alkaline solution, and titration
of iodine liberated by action of SbCl5 on KI in HC1 solution.
* Taken from Mineral Industry.
f Vide paragraph (a) of the present chapter.