1987 Volume 36 Issue 2 Pages T5-T8
Though the copperized cadmium column(Cu-Cd column) method in JIS K 0102 is excellent in precision in the determination of the total nitrogen in water, some difficulty occures by the blocking of the column in the process of the Cu-Cd column reduction of the digested sample. In this paper, the phenomenon of the blocking was discussed. When the sample in a glass bottle was digested with peroxodisulfate in high alkaline medium at 120°C, 250350 mg/l of ionic silica (after diluted to 100 ml) dissolved out from the glass wall. When the solution pH was adjusted to 8.5 prior to the reduction process, the silica up to about 200 mg/l remained stable in ionic form. And the excess was changed to colloidal form by polymerization during the standing time, and resulted in the blocking of the column.
