View source for 106.3.2.26 TM-26, Determination of Calcium Carbonate and Magnesium Carbonate in Lime and Pigment Materials

This method determines the percent chlorine in chlorinated rubber and chlorinated paraffin used in traffic paint vehicle.

==106.3.2.25.1 Reagents and Apparatus==

(a) Parr Peroxide Bomb Apparatus, 22 mL, flame ignition Macro Bomb, including ignition shield.

(b) Sodium Peroxide (Na<sub>2</sub>O<sub>2</sub>), Reagent Grade, granular, low chloride.

(c) Nitric Acid (HNO<sub>3</sub>), Reagent Grade.

(d) Silver Nitrate (AgNO<sub>3</sub>), Reagent Grade.

(e) Sodium Chloride (NaCl), Reagent Grade, dried at 105-110°C for 1 hour prior to use.

(f) Millivolt Meter equipped with a Combination Chloride Electrode.

==106.3.2.25.2 Preparation of Standard Solutions==

(a) Standard Sodium Chloride Solution (0.0100N) - Weigh 0.5844 g dried NaCl,
Reagent Grade, dissolve in water and dilute to 1L.

(b) Standard Silver Nitrate Solution (0.01N) - Weigh 1.699 g AgNO<sub>3</sub>, Reagent Grade, dissolve in water and dilute to 1L. Standardize against 0.0100 N NaCl.

==106.3.2.25.3 Procedure==

(a) Weigh, to the nearest 0.1 mg., 0.40 g sample for Chlorinated Paraffin or 0.30 g sample for Chlorinated Rubber and transfer to a Parr Bomb cup which contains 15 g Na<sub>2</sub>O<sub>2</sub>. Thoroughly mix the contents of the fusion cup with a stirring rod, wipe the rod with a small piece of filter paper and place the paper in the cup. Place the bomb assembly in the protective shield and fire strongly with a Bunsen burner for 20 minutes. Cool to room temperature and disassemble.

NOTE: If difficulties arise in obtaining complete combustion of Chlorinated
Paraffin samples, small amounts of powdered sucrose or powdered NaNO<sub>3</sub> may be mixed with the Na<sub>2</sub>O<sub>2</sub> and sample the fusion cup prior to ignition. However, the total combustible matter should not exceed 0.5 g.

Rinse the bomb cover into a 600-mL beaker with about 150 mL of water, place the cup on its side in the beaker, cover with a watch glass and warm gently until solution of the fused material is complete. Remove the cup and rinse well with water. Add HNO<sub>3</sub> in small increments until the solution is acid to methyl orange. Add 5 mL HNO<sub>3</sub> in excess and warm gently until solution is complete. Filter through a coarse paper into a 1000-mL volumetric flask, washing well with hot water. Allow to cool to room temperature and dilute to volume with water.

(b) Transfer a 50-mL aliquot to a 250-mL beaker and determine percent chlorine by
potentiometric titration.

(c) Perform a blank determination following the procedure given in (a) and (b) above,
omitting only the addition of sample.

==106.3.2.25.4 Calculation and Report==

Report percent chlorine to the nearest 0.1% as follows:

::% Chlorine (Cl) =<math>100 \times \frac {(A - B) \times C \times 0.709}{D} </math>

Where:
:A = milliliters of AgNO<sub>3</sub> solution to titrate sample,
:B = milliliters of AgNO<sub>3</sub> solution to titrate blank,
:C = normality of AgNO<sub>3</sub> solution,
:D = grams of the sample.


[[Category:106.3.2 Material Inspection Test Methods]]