The Students' Guide in Quantitative Analysis - Free Ebooks Library

DETEliMKNATlON OF SULPHUK, ETC. 83
A. Dissolve 10 grms. KCIOj in 200 ex. HA place in a
500 c.c. fiask, add 5 grms. fine borings, boll and add 60 ex.
HCl. little by little, boiling until the Fe dissolves
and
4KC10j+i2tIC1^4KCl+3C10,+9Cl+6H,0,
3Fe+C10.+Cl+4HCl=Fe,a6+2H,0.
Evaporate, dry on water-bath to insure oxidation of sul-
phur. Thorough dryness is unnecessary, since SiO^ does
not interfere in acid solution with the precipitation of
BaSO^. Then add to ex. HCl+30 c.c. H,0, and digest
on water-bath until all the FeXU is dissolved. Then add
20 c.c. iW, filter, and wash thoroughly. Add 2 ex. of a
saturated solution of BaCL (enough to precipitate the
I-I,SO, from 0.1 grm. S); after cooling add 5 c.c. NH.,HO,
stir and let stand 24 hours. Filter, and wash by decanta-
tion with cold water two or three times, and then tho-
roughly with hot water. Dry, ignite, and weigh. If the
precipitate shows traces of iron after ignition, purify by so-
lution in HjSO^.
B. For the determination of phosphorus dissolve the
pig-iron in the same manner, and dry at 140"' C ; some
anhydrous Fe,0, will remain with the SiO= ; add water,
filter, fuse residue with a Uttle KHSO^, soften with H,SO„
and dissolve in water. Filter from the SiO„ and determine
it as a check on the main analysis. Add fdtrate to mam
one, and determine the P,0;by means of ammonium molyb-
date, as in Analysis No. 21.*
2. Method of Dh. T. M. Drqwn. See Am. Ckem., Vol.
IV, p. 425.
Treat 5 grms. of borings in a flask with HCl, and pass
the H,S and PH, formed through a series oi three bottles
containing a solution of K,Mn,0,(i grm. to 200 ex. H,0)
this ceases,
Avoid a very rapid evolution of the gas ;
when
: