2740.     PRCHLÍK, J., AND OTTA, K.  [Determination of Low Concentrations of Carbon Monoxide in Flue Gases by the Combustion Method.]  Paliva a voda, vol. 30, 1950, pp. 218-219; Chem. Abs., vol. 44, 1950, p. 11059.

        I₂O₅ method has disadvantages:  I₂O₅ is hygroscopic; it is very difficult to determine when I₂O₅ is exhausted; the method consumes considerable time; it is difficult to obtain reliable results when CO is above 0.1%.  To obviate the mentioned difficulties, the authors designed gas absorption apparatus using a modified combustion method.  The flue gases are measured in a 1,000-ml. gas burette containing saturated Na₂S as confining liquid.  The gases enter a scrubber with 30% KOH to remove CO₂ and safety wash bottle with 0.005 N Ba(OH)₂ and then are led over granular refractory material 3-10 mm. in size in a Mars-tube-furnace held at about 900°.  The products of combustion, with formed CO₂, are absorbed in a series of 3 washing bottles, each one containing 20 ml. 0.005 N Ba(OH)₂.  After the run, the excess of Ba(OH)₂ is titrated back with 0.005 N oxalic acid to phenolphthalein (0.2 gm. phenolphthalein in 100 ml. 70% EtOH).  Before actual determination, the apparatus is flushed with 300 ml. CO-free air.  During the run the gas is bubbled through the tube furnace at a rate of 1-2 bubbles per sec.  Ba (OH)₂ is titrated back to the first disappearance of color.  The sum of the 3 wash bottle titrations gives the total CO content in flue gases.  The mixing of Ba(OH)₂ during titration is accomplished with CO-free air.  The accuracy is ±0.002%; the range, 0.002-0.5%; and the time required, 2 hr.