(3)Vinyl chloride-propylene copolymer content of aqueous extract -(i)Principle. The vinyl chloride-propylene copolymer content of the aqueous extract can be determined by determining the organic chlorine content and calculating the amount of copolymer equivalent to the organic chlorine content. The organic chlorine content is the difference between the total chlorine content and the ionic chlorine content.(ii)Total chlorine content. A weighed sample is extracted with water at 150 °F for 2 hours, filtered, and the volume of filtrate is measured (A milliliters) as described in paragraph (d)(2) of this section. Two drops of 50 percent by weight sodium hydroxide solution are added to prevent loss of chloride from ammonium chloride, if present, and the solution is evaporated to approximately 15 milliliters. The concentrated filtrate is quantitatively transferred to a 22-milliliter Parr bomb fusion cup and gently evaporated to dryness. To the contents of the cup are added 3.5 grams of granular sodium peroxide, 0.1 gram of powdered starch, and 0.02 gram potassium nitrate; and the contents are mixed thoroughly. The bomb is assembled, water is added to the recess at the top of the bomb and ignition is conducted in the usual fashion using a Meeker burner. The heating is continued for 1 minute after the water at the top has evaporated. The bomb is quenched in water, rinsed with distilled water, and placed in a 400-milliliter beaker. The bomb cover is rinsed with water, catching the washings in the same 400-milliliter beaker. The bomb is covered with distilled water and a watch glass and heated until the melt has dissolved. The bomb is removed, rinsed, catching the rinsings in the beaker, and the solution is acidified with concentrated nitric acid using methyl purple as an indicator. The beaker is covered with a watch glass, and the contents are boiled gently for 10-15 minutes. After cooling to room temperature the solution is made slightly alkaline with 50 percent by weight sodium hydroxide solution, then acidified with dilute (1:5) nitric acid. Then 1.5 milliliters of 2 N nitric acid per 100 milliliters of solution is added and the solution is titrated with 0.005 N silver nitrate to the equivalence potential end point using an expanded scale pH meter (Beckman Model 76, or equivalent). A complete blank must be run in duplicate. Calculation: View Image
where:
A = volume of filtrate obtained in extraction.
B = milliliters of silver nitrate solution used in sample titration * normality of silver nitrate solution.
C = milliliters of silver nitrate solution used in blank titration * normality of silver nitrate solution.
(iii)Ionic chlorine content. A weighed sample is extracted with water at 150 °F for 2 hours, filtered, and the volume of filtrate is measured (A milliliters) as in paragraph (d)(2) of this section. Two drops of 50 percent by weight sodium hydroxide solution are added and the solution is evaporated to approximately 150 milliliters. The solution is quantitatively transferred to a 250-milliliter beaker, methyl purple indicator is added, and the solution is neutralized with 0.1 N nitric acid. For each 100 milliliters of solution is added 1.5 milliliters of 2 N nitric acid. The solution is titrated with 0.005 N silver nitrate to the equivalence potential end point, using the expanded scale pH meter described in paragraph (d)(3)(ii) of this section. A complete blank must be run in duplicate. Calculation: View Image
where:
A = volume of filtrate obtained in extraction.
D = milliliters of silver nitrate solution used in sample titration * normality of silver nitrate solution.
E = milliliters of silver nitrate solution used in blank titration * normality of silver nitrate solution.
(iv)Organic chlorine content and vinyl chloride-propylene copolymer content of aqueous extract. The organic chlorine content and the vinyl chloride propylene copolymer content of the aqueous extract is calculated as follows:(a)Organic chlorine content. Milliequivalents of organic chlorine in aqueous extract of 100 grams of sample equal milliequivalents of total chlorine in aqueous extract of 100 grams of sample (as calculated in paragraph (d)(3)(ii) of this section) minus milliequivalents of ionic chlorine in aqueous extract of 100 grams of sample (as calculated in paragraph (d)(3)(iii) of this section).(b)Vinyl chloride-propylene copolymer content. Milligrams of vinyl chloride-propylene copolymer in aqueous extract of 100 grams of sample equal milliequivalents of organic chlorine in aqueous extract of 100 grams of sample (as calculated in paragraph (d)(3)(iv)(a) of this section) multiplied by 84.5. Note: The conversion factor, 84.5, is derived from the equivalent weight of chlorine divided by the chlorine content of the heptane extractable fraction.)