Measurements of carbon dioxide with the air-gap electrode. Determination of the total inorganic and the total organic carbon contents in waters.

Ruthenium(II) reacts with 3-(2-pyridyl)-5.6-diphenyl-1,2.4-triazine (PDT) in water-alcohol solution at pH 5 to give a magenta-colored cationic complex having an absorption peak at 485 nm. The color is fully developed by heating at 85° C for 30 min. The system conforms to Beer's law; the optimal concentration range for measurement at 1.00-cm optical path is about 0.5–3.4 p.p.m. of ruthenium. The molar absorptivity is 2.1 · 10⁴ 1 mole^-1 cm^-1. The effects of reagent concentration, heating temperature and time, pH, and alcohol concentration have been studied. Common anions do not interfere. Separation from interfering cations is effected by distillation and recovery of ruthenium tetroxide. Spectrophotometric methods of continuous variations and of mole ratios, and elemental analysis of solid salts isolated from solution, indicate a ruthenium-to-PDT stoichiometry of 1:2, the PDT acting as a tridentate ligand.