In this article, parameters and states of a laboratory-scale nylon 612 reactor model (Schaffer et al. Ind. Eng. Chem. Res. 2003, 42, 2946-2959; Zheng et al. Ind. Eng. Chem. Res. 2005, 44, 2675-2686; and Campbell, D. A. Ph.D. Thesis, Department of Mathematics and Statistics, McGill University, Montreal, Quebec, Canada, 2007) are estimated using a novel approximate maximum likelihood estimation (...