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Binding equilibria of a water-soluble chelating polymer, poly(R-acethylaminoacrylic acid), with divalent metal ions (Co(II), Ni(II), Cu(II), Zn(II), Pb(II)) were measured by a batch ultrafiltration method in the pH range 4-6. It was shown that the binding equilibrium curves were reasonably well represented by the complexation model accounting for the formation of three kinds of complexes (LM + , L 2 M, and L 2 M(HL) 2 ) proposed previously. The equilibrium and successive stability constants were determined by fitting the binding curves calculated from the model to the experimental ones at every solution pH. The variations of the average coordination number depending on solution pH and metal ion concentration were well explained on the basis of the relative concentration of each complex to total polymer.

A rare case of descending necrotizing mediastinitis (DNM) secondary to a nontraumatic retropharyngeal abscess is reported. Even in the era of antibiotics, the mortality of DNM is still around 40%. In spite of drainage of a localized neck abscess, and the administration of systemic antibiotics, the retropharyngeal abscess extended to the pericardial and pleural cavities. Several drainage procedures and thoracotomies were performed to treat the bilateral empyemas and purulent pericarditis. The patient was discharged on hospital day 52. Computed tomography was used to follow the progression of disease, and assess the efficacy of treatment. DNM is a very aggressive form of mediastinitis. The importance of proper mediastinal drainage, as well as the systemic administration of antibiotics, must be emphasized.

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