Mercury low pressure

Benzoyl azide (1 g, 6.8 mmol) and 6-methoxy-5,6-dihydropyran (11.4 g, 100 mmol) dissolved in acetonitrile (100 mL) are placed in 10 quartz test tubes and irradiated using light of wavelength 254 nm (mercury low pressure lamp) for 9h using a merry-go-round photoreactor. After removing the solvent and the olefin excess by vacuum evaporation, the reaction mixture... 

Figure 2 Emission properties of a) mercury low-pressure lamp (strong 254 line), b) mercury high-pressure lamp and c) RPR-3(XX)A lamp for Rayonet photoreactors (3(X) nm line).

UV-Illumination. was carried out in inert atmosphere (argon) by using an ozone free mercury low pressure UV lamp (Heraeus Noblelight 254 nm) with a power density of 1.35 mW/cm2. One half of the substrate was shaded during illumination. 

The UV and visible fluorescence of Er3+ in our glasses is much weaker than that of Tm +. The fluorescence was observable only in phosphate glasses, with 382 nm excitation (from a xenon source) and 255 nm excitation (from a mercury low-pressure lamp). In Table 8. we present the wavelengths of fluorescence together with the transition assignments obtained under excitation at 382 and 255 nm. 

To monitor the chemiluminescence (CL) from the composites, thin films of the samples were irradiated in the air at 23°C with light from a mercury low-pressure lamp, 80% of the radiation of which is 254 nm monochromatic light. The irradiated samples were placed in the CL... 

The irradiation of films fi"om the mixtures of VAVAC and PHB as well as films from individual VAVAC, by the light with X=254 nm of a mercury low pressure lamp DB-60 or by the light with 290 run of a xenon lamp in the machine SUNTEST XLS + , leads to a complex change in the absorption spectra in the near UV- and visible area at the begirming of irradiation optical density sharply decreases and then slowly increases approaching with the prolonged irradiation to its stationary value. 

FIGURE 1 Changes in the relative optical density in the area of 357 nm during irradiation in air by the light of a mercury low pressure lamp DB-60 with X=254 nm of the films with the thickness of 0.2 mm from VAVAC (1) and from the mixtures of VAVAC with 10 (2) or 20% PHB (3). Points - experimental data, curves - calculations by Eq. (1). 

The commercial form of Cartesian manostat, model 7A, is depicted in Fig. II, 23, 7 it is normally charged with mercury except for very low pressures when di-w-butyl phthalate is employed. The manostat is highly sensitive in its action furthermore, once the pressure has been set in the instrument, the system may be shut down without disturbing the setting. 

In molecular distillation, the permanent gas pressure is so low (less than 0 001 mm. of mercury) that it has very little influence upon the speed of the distillation. The distillation velocity at such low pressures is determined by the speed at which the vapour from the liquid being distilled can flow through the enclosed space connecting the still and condenser under the driving force of its own saturation pressure. If the distance from the surface of the evaporating liquid to the condenser is less than (or of the order of) the mean free path of a molecule of distillate vapour in the residual gas at the same density and pressure, most of the molecules which leave the surface will not return. The mean free path of air at various pressures is as follows —... 

When exhausting desiccators, a filter flask trap (see Fig. 77, 19, 2) should always be inserted between the desiccator and the pump. The vacuum should be applied gradually and should not exceed about 50 cm. of mercury for models (a), (6) and (d). These desiccators may withstand lower pressures, but it is generally considered unsafe to exhaust below this pressure unless the precaution be taken of surrounding the desiccator by a cage of fine-mesh steel wire collapse of the desiccator will then do no harm.J Models (c) and (e) may be exhausted to about 20 mm. of mercury a steel wire cage must be provided for this low pressure. 

Isothiazole itself (283), Rx = Rj = Rj - H, is converted to thiazole in 7% yield, in propylamine as solvent using a low-pressure mercury lamp (642). 

In practice, o2one concentrations obtained by commercial uv devices ate low. This is because the low intensity, low pressure mercury lamps employed produce not only the 185-nm radiation responsible for o2one formation, but also the 254-nm radiation that destroys o2one, resulting in a quantum yield of - 0.5 compared to the theoretical yield of 2.0. Furthermore, the low efficiency (- 1%) of these lamps results in a low o2one production rate of 2 g/kWh (100). 

Mercury from cinnabar ore 225 tons ore/day (95% recovery) (2) 18,0 ft. diam, 8 hearth furnaces Furnaces fired on hearths 3 to 7, inclusive retention time of 1,0 hr, furnaces are oil-fired with low-pressure atomizing air burners all air, both primary and secondary, introduced through the burners draft control by Monel cold-gas fans downstream from mercury condensers. 

One way of implementing the UV disinfection process at existing activated sludge plants involves suspending the UV lights (in the form of low-pressure mercury arc UV lamps with associated reflectors) above the secondary clarifiers. The effluent is exposed to the UV radiation as it rises over the wire in a thin film. 

In contrast to the low-pressure lamps (1—130 Pa) which primarily emit at the resonance line at A = 254nm, high-pressure lamps (lO —10 Pa) also produce numerous bands in the UV and VIS regions (Fig. 16). Table 3 lists the emission lines and the relative spectral energies of the most important mercury lamps (see also [44]). The addition of cadmium to a mercury vapor lamp increases the numbei of emission lines particularly in the visible region of the spectrum [45] so that it i. also possible to work at A = 326, 468, 480, 509 and 644 nm [46]. 

Fig. 16 Relative intensity distribution of a mercury NK 4/4 low pressure lamp (A) and of a mercury St 41 or St 48 lamp (B).

A solution of 0.17 g (51) in 160 ml benzene is stirred magnetically and irradiated for 6 hr with a Hanau NK 6/20 low-pressure mercury lamp (main emission at 2537 A) placed in a central water-cooled quartz tube. Cyrstalliza-tion of the crude product gives 0.15 g (52) (88%). 

With 2537 k-Light. 1 g (140) in 140 ml anhydrous dioxane is irradiated for 20 hr at room temperature with a Hanau NK 6/20 low-pressure mercury lamp placed in a central water-cooled quartz finger. 0.19 g of (141) crystallize from the crude reaction mixture as described above. Chromatography of the residual material on silica gel with benzene-ethyl acetate (4 1) gives 0.29 g of B-nortestosterone acetate [(142) 28.5 %] and starting material (140). 

Because of quite poor color rendition and difficulty in safe disposal of expended lamps, low pressure sodium fixtures are less desirable than high pressure sodium fixtures and are seldom recommended for production facilities. High pressure sodium fixtures are particularly attractive for illuminating large open areas. At locations where power cost is low and where many fixtures are required due to equipment shadowing, mercury vapor fixtures often are preferred because of their lower initial cost, lower replacement lamp cost, and better color rendition. 

In 1970, Hiraoka reported that 2-cyanopyrrole, irradiated in methanol with a low-pressure mercury arc for 20 h, gave a mixture of 3-cyanopyrrole and pyrrole-2-carbaldehyde [70JCS(CC)1306]. l-Methyl-2-cyanopyrrole (38) also gave this reaction (Scheme 15) [71JCS(CC)1610]. In this case, the author isolated the product of the isomerization 39, the product of the shift in C-2 of the IV-methy 1 group 40, and a third product that was assumed to be derived from the addition of methanol to the Dewar pyrrole 41. The reaction depends on the temperature used in fact, no reaction occurred when the reaction was performed at -68°C. This result is in agreement with the presence of a thermal-activated step [78JCS(CC)131]. More... 

The irradiation of isothiazole with a low-pressure mercury arc leads to the formation of thiazole [69JCA(CC)1018], The photochemical behavior of alkyliso-thiazoles has been studied. 3-Methylisothiazole gave 2-methylthiazole in a low yield. 4-Methylisothiazole was converted into 4-methylthiazole, and 5-methyliso-thiazole gave a mixture of 5-methylthiazole (55%) and 4-methylisothiazole (Scheme 38) (72T3141 93JOC3407). Either a ZI (72T3141) or an ICI mechanism was invoked to justify these reactions (93JOC3407). 

A solution of phenol (188 mg, 2 mmol) and benzonitrile (2.06 g, 20 mmol) in McCN (20 mL) was degassed by bubbling nitrogen through it and irradiated with a 16-W low-pressure mercury arc lamp (Applied Photophysics Ltd, APQ40) for 24h. The crude product was separated by flash chromatography (EtOAc/ petroleum ether 1 5) to give yellow crystals yield 79 mg (20%) mp 53-55 C. 

For very low pressures, a diffusion pump is used with a rotary pump as the first stage. The principle of operation is that the gas diffuses into a stream of oil or mercury and is driven out of the pump by molecular bombardment. 

---