Document NGEX1God5BeO4Ya7VwmK1o8Q

TENNECO CHEMICALS, TNG. TENNECO INTERMEDIATES DIVISION T.A.M. 4-3 T.A.M. 4-3 Specific Use: Burlington Compound Plant- Dale Issued: May, 1973 DETERMINATION OF LEAD CONTENT OT DIBASIC LEAD STEARATE, TR1BASIC LEAD SULFATE AND COMPOUNDS CONTAINING THESE STABILIZERS ' APPLICATION This is a gravimetric assay technique for the determination of lead content in dibasic lead stearate, tribasic lead sulfate and compound dry blends containing these stabilizers. The method is based on the digestion of a sample in 1:1 HNOg/l^SO followed by oxidation with driving off the HNOg and precipitating'the lead as the sul fate . APPARATUS 1. Beakers, graduated, 400 ml 2. Ifot plate 3. Crucibles, gooch, porcelain (Ace Scientific, Cat. #11-6770, EDP-07) 4. Asbestos, long fiber (acid-washed )(Matheson, Cat. #AX1760) 5. Glass beads 6. Flask, filter, 500 ml 7. Wash bottles, polyethylene 8. Speedyvap watch glasses 9. Analytical balance with readout to 0.1 mg 10. Furnace, muffle 11. Desiccator 12. Glass stirring rod 13. Thongs 14. Vacuum pump , 15. Rubber gloves REAGENTS 1. Sulfuric acid, reagent grade 2. Nitric acid, reagent grade 3. 10% sulfuric acid solution (carefully transfer 100 ml of ll^SO* into 400 mJ of water - cool and make up to 1,000 ml, mix well) 4. Isopropyl alcohol, reagent grade 5. Demineralized water 6. 30% hydrogen peroxide solution COLOR!TE 014704 T.A.M. 4-3 Page 2 Procedure 1. Weigh 0.5 - 0.8 gm duplicate samples in 400 ml beakers and record to the nearest 0.1 mg (for compounds 2.0 gm). 2. /\dd 50 ml of IlNO-j and 25 ml of H2SO4, and a few glass beads. Place watch glasses on top of the beakers. 3. boil the solution until the solution stops boiling (Note 1. ). 4. Remove beakers from the hot plate. Add 30% H2O2 from a wash bottte until the oxidation of HNO3 is complete (Note 2. ). 5. Add enough demineralized water to bring the volume of the solution to 125 ml and boil for 15 minutes (Note 3. ). 6. Remove from heat, cool and add 50 mi of isopropyl alcohol from a wash bot tle. Refrigerate the solution, 7. After cooling, filter the solution through a previously-fared gooch cruc ible fitted with asbestos filters. Wash the filtrate with a 10% II2SO4 so lution. 8. Place the crucibles on a hot plate ( 80C, covered with an asbestos plate) for one hour. 9. Place the crucibles in a desiccator and allow to cool. 10, Re-weigh the crucibles, determine the precipitate weight and calculate the lead content. CALCULATION % Pb = A x 0.683 x 100 B A = Precipitate Weight (gm) B - Sample Weight (gm) NOTE 1. When solution begins to boil, it will emit nitric oxide fumes. These fumes are brownish in color. At a certain point in the boiling, the nitric oxide will stop being emitted and the solution will stop boiling. When analyzing compounds, make sure sample is completely digested by adding small incre ments of HNO3. 2. Be sure to add only small amounts of the 30% H2O2 at a time from a wash bottle. The oxidation of HNO3 is very violent. Heat generated from this reaction will cause the mixture to boil over and a loss of the precipitate will result. 3. Swirl beaker by hand once in a while, until the mixture begins to boil. Written by: W.L. Stewart Issued H. IK Carr Supervisor - Quality Control COLORXTE 014705