Chromium Analysis in Cast Iron
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Svapnesh ParikhChromium Analysis in Cast Iron
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Svapnesh ParikhIS 12308 (Part 8) : 1997
Indian Standard
METHOD FOR CHEMICAL ANALYSIS OF
CAST IRON AND PIG IRON
PART 8 DETERMINATION OF CHROMIUM BY PERSULPHATE OXIDATION METHOD
( FOR CHROMIUM 0.1 TO 28 PERCENT)
1 SCOPE 5.2.2 NitricAcid, rd = 1.42 (conforming to IS 264).
1.1 This standard (Part 8) covers the method for 5.2.3 Dilute Hydrofluoric Acid, 40 percent (v/v).
determination of chromium in the range from 0.1
to 28 percent in alloy cast iron and pig iron. 5.2.4 Dilute Sulphuric Acid, 1 : 5 (v/v).
2 REFERENCE 5.2.5 Potawium BkulphatelPotasskm Pyrosul-
phates, Solid
The following Indian Standards are necessary ad-
juncts to this standard: 5.2.6 Silver Nitrate, 0.5 percent (rn,‘v).
IS No. Title
5.2.7 Ammonium Persulphate, 15 percent (m/v).
264 : 1976 Nitric acid (second revision)
5.2.8 Potassium Permanganate Solution, 0.1 N.
1070 : 1992 Analytical grade water (third
revision) Dissolve 3.2 g of potassium permanganate in one
litre of water and keep in the dark for several days.
3 SAMPLING Filter the solution through a sintered glass crucible
and store in a well stoppered dark coloured bottle.
The sample shall be drawn and prepared as
Standardise the solution as follows:
prescribed in the relevant Indian Standard.
Dissolve 0.134 g of extra pure sodium oxalate
4 QUALITY OF REAGENTS crystals, dried for 1 hour at 105°C in a 200 ml of
Unless specified otherwise, analytical grade dilute sulphuric acid (1 : 50). Heat to 70°C.
reagents and reagent grade water (see IS 1070) shall Titrate with potassium permanganate solution
be employed in the test. until one drop produces a permanent pink
colouration.
5 DETERMINATION OF CIIROMIUM BY
[ 1 ml of $ KMn04 = 0.006 7 g of Na2 (COO)2]
PERSULPEMTE OXIDATION METIIOD
5.1 Outline of the Method 5.2.9 Dilute Hydrochloric Acid, 1 : 3 (v/v).
Sample is dissolved in sulphric acid - phosphoric 5.2.10 Standard Ferrous Ammonium Sulphate,
acid mixture and chromium (III) is oxidised to (O’IN).
Chromiu’m (VI) by ammonium persulphate in
presence of silver nitrate as catalyst. Chromium is Dissolve 40 g of ferrous ammonium sulphate in 500
then reduced to Chromium (III) by excess of fer- ml of cold dilute sulphuric acid (5 percent) and
rous ammonium sulphate solution and the excess dilute to one litre with the same (see Note 1).
ferrous ammonium sulphate is titrated with stand- Standardize the solution as follows:
ard potassium permanganate solution. Transfer 180 ml of water. 12 ml of dilute sulphuric
5.2 Reagents acid (1: 1) and 5 ml of phosphoric acid into a 500 -
ml Erlenmeyer flask. Add 20 ml of ferrous am-
5.2.1 Sulphuric Acid monium sulphate solution and finally add 1 to 2
drops of 1,lO phenanthroline indicator solution.
Phosphoric Acid Mixture
Titrate the ferrous ions with 0.1 N KMn04 sttndard
Add slowly, while stirring, 160 ml of sulphuric acid solution (5.2.8) while swirling the flask. Continue
to 600 ml water. Cool and add 80 ml of phosphoric until the pink colour changes to clear green and
acid. persists for atleast 60 s.