Laboratory ozonation system

Ozone (approximately 1 ml.) was prepared by corona discharge in a laboratory ozonizer and condensed in the receiver tube, R. Tube R was then attached to the apparatus, Ti, which was cooled in liquid nitrogen. The system was evacuated, and ozone was distilled successively into Ti, T2, and the U-tube section of the apparatus. A, with the system open to the pump. The multiple distillation ensured removal of oxygen. Results indicate that oxygen is easily removed from liquid ozone and that a single distillation through a re-entrant trap is sufficient. 

Ozone is usually produced on demand from a laboratory ozone generator, and a procedure for the treatment of excess ozone should be included in the experimental plan. Small to moderate amounts of excess ozone can be vented to the fume hood or other exhaust system. When large amounts of excess ozone are anticipated, the excess gas should be passed through a series of traps containing a 1 to 2% solution of potassium iodide or other reducing agent before venting to the fume hood. ... 

Ion chromatography is used at the City of Lincoln, Nebraska, Water Treatment Plant Laboratory to analyze water samples taken from sampling sites in the distribution system around the city. The common anions determined by IC are not only nitrate, nitrite, fluoride, and sulfate, but also bromate. Bromate is found in the water because the Lincoln plant treats the water with ozone. Adding ozone to the water oxidizes any bromide to bromate. Bromate is regulated at 10 parts per billion (ppb) its concentration must be determined. 

On a laboratory scale the dehydration of nitric acid with phosphorous pentoxide is a convenient route to dinitrogen pentoxide (Equation 9.2). Isolation is achieved by sublimation and collection in a cold trap at -78 °C, but the quality and yield of dinitrogen pentoxide is poor if the system is not continually flushed with a stream of ozone, a consequence of facile decomposition to dinitrogen tetroxide. 

Most of the reactions the inorganic chemist encounters in the laboratory involve ionic species such as the reactants and products in the reactions just discussed or those of coordination compounds (Chapter 13). However, in the atmosphere there are many free radical reactions initiated by sunlight. One of the most important and controversial sets of atmospheric reactions at present is that concerning stratospheric ozone. The importance of ozone and the effect of ultraviolet (UV) radiation on life has been much discussed. Here we note briefly that only a small portion of the sun s spectrum reaches the surface of the earth and that parts of the UV portion that are largely screened can cause various ill effects to living systems. 

For the experimenter in the laboratory, not only do materials have to be chosen on the basis of their corrosion-resistance, but also for their effect on ozone decay. Some metals (e. g. silver) or metal seals enhance ozone decay considerably. This can be especially detrimental in drinking water and high purity water (semiconductor) ozone applications, causing contamination of the water as well as additional ozone consumption. Moreover, the latter will cause trouble with a precise balance on the ozone consumption, especially in experiments on micropollutant removal during drinking water ozonation. With view to system cleanliness in laboratory experiments, use of PVC is only advisable in waste water treatment, whereas quartz glass is very appropriate for most laboratory purposes. 

In the laboratory batch ozonation is easy to apply, whereas multi-stage continuous-flow systems are difficult to handle (Method 1). However, mainly due to large liquid flow rates the inverse situation is valid for many full-scale applications. Often three oxidation reactors in series are found in waste water ozonation (cf. Table A 3-3). The advantage of a multi-stage CFSTR system - or even a batch system - lies in their faster reaction rates compared to a single CSTR due to the reduced axial/longitudinal mixing. 

Osmium tetroxide, like the skunk, carries its own warning system-a strong odor described variously as resembling chlorine, bromine, or ozone. Clearly, a commonsense approach to the use of this reagent in an efficient hood is called for, and under these conditions osmium tetroxide should be regarded as no more dangerous than many other reagents found in daily use in the laboratory. 

Laboratory systems containing hydrocarbons and NOa in air were irradiated and analyzed for oxidants. Four hydrocarbons that produced large amounts of HCHO per mole of reacted hydrocarbon were 1,3,5-trimethylbenzene, propylene, 1-butene, and ethylene. Hydrogen peroxide was detected in all four systems. Ozone was the major oxidant in these systems. Figure 2 shows the fate of a mixture of 5.5 ppm of ethylene (C2H4) and 2.2 ppm of NO2 irradiated at 3660 A for 11 hours. The O3... 

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