Test for Iron on the fiber:
Reagents: Nitric Acid 5% or 10%
w/w Analytical grade.
Potassium Thiocyanate
Solution 10% w/w made
by dissolving 10 g
Potassium thiocyante in 90
gram distilled water
Potassium bisulphate,
analytical grade.
Hydrogen peroxide 35% w/w.
A small sample 0.5 to 1.0 gram of fiber is
placed on a watch glass and then spotted with 1-2 drops of nitric acid
(5%) and allowed to stand for 2-3 minutes so that any iron present is
oxidized to ferric ions. To detect ferric ions, 2 to 4 drops of potassium
thiocyanate (10%) are added.
If no color forms then no iron is present. A
red color indicates iron is present and the intensity of the color
indicates the amount. A pink color indicates low concentrations and a wine
red color high concentrations.
Potassium Ferrocyanide test:
A small sample of fabric on a watch glass is
spotted with dil Hydrochloric acid(10%). The acidified area of the fabric
is then spotted with dil.Pot.ferrocyanide (1% solution freshly prepared).
A dark blue color indicates the presence of iron.
Test for Copper:
Copper tetramine test:
The fabric sample is properly ashed using an
oven and the cooled ash is spotted with 5 to 10 drops of nitric acid (10%)
or hydrochloric acid or by melting with pot.bisulphate.
Add dil. Ammonia (1:1) until the ash is
alkaline. A blue color shows the presence of copper. A white background
e.g. a sheet of paper helps in observing the shade changes.
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