Document ppELpLmxo5zpob08L715e2ooE

INTER OFFICE MEMO TENNECO CHEMICALS, INC To M. rreifeld Subject Lead Assay At riemington at Burlington date April 3, 1973 Copy To./Filc J>,( y'.A. /u'/t As we concluded at an All-Disc task force meeting on 11/17/72, the atomic absorption assay method for lead is inadequate due to erratic results. Since that time, we have been successful in developing a gravimetric assay technique that is accurate and reproducible for lead analyses of 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 HNOgil^SO^, foll owed by oxidation with driving off the HNOg and precipitating the lead as the sulfate. The lead sulfate is filtered through a fared gooch crucible and dried to constant weight from which the lead content is calcu- lated (factor is 0.683). This method will be adopted as a standard proced ure. . In the attached Table I (Lead Analyses), assay results are shown for dibasic lead stearate, tribasic lead sulfate and compound dry blend. It will be noted that all dibasic lead stearate samples are in-specification but that the Eagle-Picher tribasic lead sulfate samples are somewhat low. In a round robin interchange, Eagle-Picher confirmed the low lead assays and has stated that appropriate corrective action will be taken. The compound dry blend results indicate a fairly wide spread in results (0,61% - 0.82%) versus a theoretical result of 0.74%. A laboratory-prepared dry blend assayed at 0.73%. The dry blend assay results are limited and more data is required to assess actual plant control. The lead assay method is currently being established in Burlington. Each raw material lot will be assayed for conformance to specification. Additional dry blend analyses will be performed on each 3805D lot produced, the target being six analyses per lot. Attachment. HBC/jst H.B. Carr COLORITE 014841 tabu: I LEAD ANALYSES Dibasic Lead Stearate NL Industries DS 207 Specification for Pb: 50.4% - 52.2% Compound lot Number Lot 7-112849 Sample Mix 1 tt Mix 23 IT Mix 49 TT Mix 59 Tt Lot 7-013000 Lot 7-023102 Mix 137 _ Result 50.8% Rerun (51.1%) 52.2% 51.3% 51.3% Rerun (51.2%) 52.1% 51.8% 51.4% DBLS Lot Numbe: NL Lot 2850 TT TT TT TT Tt tt TT Tt TT T! TT TT NL Lot 2875 NL Lot 2879 Tribasic Lead Sulfate Eagle-Picher Epistatic 100 Specification for Pb: 83.5% - 84.5% Compound Lot Number Lot 7-112849 Sample Mix 1 tt Mix 23 T! Mix 49 TT Mix 60 NL Industries Tribase Specification for Pb: 82.2% - 83.3% (Tenneco) Result (Eagle-Picher) Result 81.3% (EP Lot 27A-505) 81.9% 81.2% Rerun (81.5%) (EP Lot 27A-505) 82.0% 81.0% (EP Lot 27A-505) 82,7% (NL Lot 172255A) 81. 8% _ COLORTTE 014842 TABLE I LEAD ANALYSES , (continued) \ Dry Blend Pb content based on formulation: 0.74% (0.8% DBLS; 0.4% TBLS) Compound Lot Number -1X2849 Sample Mix 7 it Mix 8 Tf Mix 9 ii Mix 10 ii Mix 17 ii Mix 64 Lab-Prepared Dry Blend TBLS 82,7% DBLS 51.3% Result 0.82% Rerun (0.85%) 0.70% 0.75% 0.85% 0.61% Rerun (0.64%) 0.73% 0.73% COLORITE 014843