ISO 3622:1996

@ IS0
IS0 3622:1996(E)
7.1.2 Reagents
7.1.2.1 Nitric acid (HNOs), (1 + 9) solution 1).
7.1.2.2 Ammonium iron(W) sulfate [(NH4)Fe(SO&], 50 g/l solution.
7.1.2.3 Silver nitrate (AgNO$, standard volumetric solution of 0,100 mol/l (17,0 g/l) 2) 3).
7.1.2.4 Ammonium thiocyanate (NHbSCN), standard volumetric solution of 0,100 mol/l (7,61 g/l) 2).
7.1.3 Apparatus
7.1.3.1 Burette, of 50 ml capacity.
7.1.3.2 Pipette, of 50 ml capacity.
7.1.4 Procedure
Weigh, to the nearest 0,001 g, a test portion of about 0,3 g and dissolve it in 50 ml of water. Add 5 ml of the nitric
acid (7.1.2.1), followed by 50,OO ml of the silver nitrate (7.123) using the pipette (7.1.3.2). Shake well, add 2 ml of
the ammonium iron(lll) sulfate (7.122) and titrate the excess of silver nitrate with the ammonium thiocyanate
(7.124) to a permanent red endpoint.
7.1.5 Expression of results
The assay, expressed as a percentage by mass of NH&NS, is given by
7,612(5Oq - Vq)/m
is the actual concentration, in moles per litre, of the silver nitrate (7.123);
Cl
is the volume, in millilitres, of the ammonium thiocyanate (7.1.2.4) used for the titration;
V
is the actual concentration, in moles per litre, of the ammonium thiocyanate (7.1.2.4);
e2
m is the mass, in grams, of the test portion;
50 is the volume, in millilitres, of silver nitrate added (7.1.4);
7,612 is the conversion factor obtained from the mass of ammonium thiocyanate equivalent to 1 mole of
silver nitrate (i.e. 76,12) x the conversion factor for millilitres to litres (i.e. 0,001) x 100 (for percentage).
7.2 Residue after ignition
7.2.1 Specification
Maximum content of residue after ignition shall be 0,lO %
h/m).
1) This solution may be prepared from concentrated nitric acid, 69 % (m/m) (approx.) (DANGER: (C)(B)(O)). (Hazard warning
codes are defined in IS0 10349-I .)
Commercially available analysed reagent Procedures for the preparations of these materials
2) solutions are recommended.
are available in any quantita
tive analysis text.
3) This solution may be prepared from solid silver nitrate (DANGER: (C)).

---------------------- Page: 1 ----------------------
@ IS0
IS0 3622: 1996(E)
7.2.2 Procedure
Determine the percentage residue after ignition in accordance with IS0 10349-4. Weigh about 5,0 g of sample and
ignite it in a platinum crucible (600 “C + 50 OC, 4 h, 0,001 g). Cool in a desiccator and then weigh to the nearest
0,001 g.
7.3 Heavy metals content
7.3.1 Specification
Maximum content of heavy metals shall be 0,002 % (m/m).
7.3.2 Procedure
NOTE - The standard for the iron test (7.4) is prepared in the same way as the heavy metals standard.
Determine the percentage of heavy metals in accordance with IS0 10349-5. Use a test portion of I,90 g to 2,lO g,
prepared in accordance with IS0 10349-5:1992, 7.2. Use 4 ml of the heavy metals standard prepared in accordance
with IS0 10349-5:1992, 8.1 .I.
7.4 Iron content
7.4.1 Specification
Maximum content of iron shall be 0,0005 % C&m).
7.4.2 Procedure
Determine the percentage of iron in accordance with IS0 10349-5. Use a test portion of I,90 g to 2,lO g,
prepared in accordance with IS0 10349-5:1992, 7.2. Use 1 ml of the iron standard prepared in accordance with
IS0 10349-5:1992, 8.1.1.
7.5 Halide content (as Cl-)
7.51 Specification
Maximum content of halide shall be 0,06 % (m/m) [O,l % (m/m) as NH&I].
7.5.2 Reagents
7.5.2.1 Sodium hydroxide (NaOH), solid (DANGER: ((C))).
7.5.2.2 Hydrogen peroxide (H202), 67 g/l (approx.) solution.
Dilute 1 volume of 30 % hydrogen peroxide (DANGER: ((C))(O)) with 4 volumes of water.
7.5.3 Procedure
Weigh, to the nearest 0,l g, a test portion of about 1 g and dissolve it in 30 ml of the hydrogen peroxide (7.5.2.2).
Add 1 g of sodium hydroxide (7.5.2.1) (DANGER: ((C))1 and swirl until the vigorous reaction ceases. Add another
30 ml of hydrogen peroxide (7.5.2.2) and boil for 2 min. Cool and dilute to 100 ml with water. Use a 10 ml aliquot of
this test solution. Continue the procedure in accordance with IS0 10349-6:1992, clause 4, using 6 ml of the halide
standard solution A.

---------------------- Page: 2 ----------------------
Q IS0
IS0 3622: 1996(E)
7.6 pH value
7.6.1 Specification
The pH of the solution shall be between 4,5 and 6,0.
7.6.2 Apparatus
7.6.2.1 Electronic pH-meter, equipped with a glass electrode and standard reference electrode.
7.6.3 Procedure
Weigh, to the nearest 0,l g, a test portion of about 5 g and dissolve it in about 80 ml of boiled water. Dilute to
100 ml. Measure the pH of the solution at 20 OC, using the pH-meter (7.6.2.1) in accordance with the
manufacturer’s instructions.
7.7 Sulfur compounds
For us e in non-develo per solution .g. fixers), the less-sensiti ve iodi ne co nsumpt ion test is adequate, whereas for
s (e
cal silver nitrate test is red.
use In developers the more-sensi tive ammonia
7.7.1 Amount precipitated by ammoniacal silver nitrate
...