Mercury, sources

By far, the most frequently used device is the ultraviolet detector. Three types are employed (23) — single wavelength with low pressure mercury source, multiwavelength filter photomer with medium pressure mercury source, and spectrophotometer. 

In the single wavelength detector, 254 nm and 280 nm are strong lines from the mercury source and hence, are selected in most comnercial instruments. Of the three types of U.V. detectors, this one gives the lowest noise level (down to 0.00002 O.D.), but, of course, some flexibility is lost in not being able to work at other wavelengths. Nevertheless, when one purchases an instrument, this is the first detector selected. 

Fig. 2. Relative radiant intensity of halogen (A), xenon (B), and mercury sources (C).

Among the Alchemists, the Sun [Soleil] means vulgar gold. The Hermetic Philosophers call their Sulphur and Gold Sun. The Sun of the Wise with a mercurial source is the fixed part of the Matter of the Great Work, and the Moon means the volatile part. They also call Sun the fire which is within or innate to the Matter. ... 

Figure 14.15—Pulsed hollow cathode lamp background correction, a) Shape of the emission line from a hollow cathode lamp under normal operating conditions, b) the 4000 Smith-Hieftje model from Thermo Jarrell Ash uses the principle of pulsed-source correction. The mercury source and the retractable mirrors are used for calibration of the monochromator. (Reproduced by permission of Thermo Jarrell Ash.)...

The Model 835 multiwavelength filter photometer (Fig.3.44) provides energy at 254 nm with a low-pressure mercury lamp and at 280,313,334 and 365 nm with a medium-pressure mercury source. Selected wavelengths between 380 and 650 nm are also available with a quartz-iodine light source. Absorbance ranges of 0.01-2.56 AUFS are provided. Short-term noise levels are 5 X 10-s AU with the low-pressure mercury source and 1 X 10 4 AU with the other lamps. The design and dimensions of the cell are the same as for Model 840. A 24-jtzl cell is standard with the medium-pressure mercury lamp and the quartz—iodine lamp. 

The simplest spectrophotometric detector is the fixed-wavelength variety which most commonly utilizes a low-pressure mercury source with a high-... 

Photoisomerizations were carried out using a 450 watt Hanovia medium pressure mercury source, and each reaction was followed to the photo-stationary state by gas chromatographic determination of the cis/trans ratios. Twice recrystallized trans-stilbene (Aldrich), spectrophotometric grade cyclohexane, and dry, high purity carbon dioxide were used in these experiments. 

Photolysis of 2-benzoyl-1,2-dihydroisoquinaldonitrile (8) with 2537 A light in acetonitrile or benzene solution, using a high-pressure mercury source, the yield of nitrile was lower. The photolyses also produced a low yield of the aldehydic fragment corresponding to the aroyl group. 

The top 15 cm of sediments in Wisconsin lakes contained higher levels of mercury (0.09-0.24 g/g [ppm]) than sediments at lower sediment levels (0.04-0.07 g/g [ppm]). Because the lakes are not known to receive any direct deposition of mercury, it was postulated that the primary mercury source was atmospheric deposition (Rada et al. 1989). Mercury levels in surface sediments of the St. Louis River ranged from 18 to 500 ng/L (ppt) (Glass et al. 1990). Mercury was detected in sediment samples from Crab Orchard Lake in Illinois at concentrations greater than 60 g/L (ppb) (Kohler et al. 1990). 

P.V. Koval, G.V. Kalmychkov, V.F. Gelety et al.. Correlation of Natural and Technogenic Mercury Sources in the Baikal Polygon, Russia, /. Geochem. Explor. 66(1-2), 277-289, July (1999). 

R. Ferrara, B. Mazzolai, H. Edner et al.. Atmospheric Mercury Sources in the Mt. Amiata Area, Italy, Sci. Total Environ. 213(1-3), 13-23, June 10 (1998). 

Figure 13.16 Pulsed lamp for background correction. Tlie model sliown uses tlie principle of the Smith-Hieftje pulsed source background correction. The mercury source as well as the retractable mirrors are used to cahbrate the monochromator (reproduced courtesy of Thermo Jarrell Ash). Appearance of an emission line of a HC lamp as a function of its voltage.

The ESR spectrum of polypropylene irradiated with a medium pressure mercury source in vacuo exhibits four narrow bands equally spaced. This is due to the methyl radical superimposed on the spectrum, believed to be a sextet, assigned to --CH2— CH—CH2—, and a quartet which overlap [31, 32]. The quartet has been attributed to... 

Fig. 12. Cis—trans photo-isomerization of poly butadiene, cis O medium pressure mercury source, lower scale, low pressure mercury source, upper scale trans A medium pressure mercury source, lower scale [reproduced with permission from Ref. 48].

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