Ultra-violet light

UPS Ultraviolet photoelectron spectroscopy Light (ultra- violet) Photoelectron... 

BHC is manufactured by chlorination of benzene in the presence of ultra-violet light. The gamma-isomer is obtained from the crude mixture by selective crystallization, and forms colourless crystals, m.p. I13" C. U.S. production 1980 400 tonnes. 

In the electromagnetic spectrum, the ultra violet region is between that of X-rays and visible light. This corresponds to the energies hv ot one hundred to a few tens of electron-volts (wavelengths from 180 to 400 nm). 

Ozone, O3, is found in trace quantities in the upper atmosphere where it is believed to be formed by the photochemical dissociation of oxygen molecules by the intense ultra-violet light from the sun ... 

Braude, Ultra-Violet Light Absorption and the Structure of Organic Compounds Annual Reports, 42, 105 (1945). ... 

Since acetal resins are degraded by ultra violet light, additives may be included to improve the resistance of the polymer. Carbon black is effective but as in the case of polyethylene it must be well dispersed in the polymer. The finer the particle size the better the ultra violet stability of the polymer but the poorer the heat stability. About 1.5% is generally recommended. For white compounds and those with pastel colours titanium dioxide is as good in polyacetals as most transparent ultraviolet absorbers, such as the benzophenone derivatives and other materials discussed in Chapter 7. Such ultraviolet absorbers may be used for compounds that are neither black, white nor pastel shade in colour. 

According to Grewe, colchicine on exposure to ultra-violet light changes to an isomeride, needles, m.p. 220°, which he has named lumieolehieine. 

EtOH) solutions show a blue fluorescence in ultra-violet light. It contains one methoxyl, one methylenedioxy and one methylimino group. The following salts have been prepared B.HCl, m.p. 164r-5°, 23°... 

Lunamarine, CjgHjjO N, probably identical with the limacridine of Dieterle and Beyl. M.p. 245-6°, [a]D 0°. Solutions in alcohol fluoresce blue in ultra-violet light. ... 

Other benefits of light-colored roofs include a potential increase in their useful life. The daily temperature fluctuation and concomitant expansion/coii-traction of a light-colored roof is less than that of a dark one. Also, materials degradation because of absorption of ultra-violet light is temperature-dependent. Thus, cooler roofs may last longer than... 

J. A. Radley and J. Grant, Fluorescence Analysis in Ultra-violet Light, Chapman and Hall, London, fourth edition, 1954. 

Lippert and Vogel (Ref 7) asserted, on the other hand, that on irradiation with high intensity ultra-violet light, nitrocompds undergo dissociation into free radicals ... 

Purification of anthracene. Dissolve 0-3 g. of crude anthracene (usually yellowish in colour) in 160-200 ml. of hexane, and pass the solution through a column of activated alumina (1 6-2 X 8-10 cm.). Develop the chromatogram with 100 ml. of hexane. Examine the column in the light of an ultra-violet lamp. A narrow, deep blue fluorescent zone (due to carbazole, m.p. 238°) will be seen near the top of the column. Immediately below this there is a yellow, non-fluorescent zone, due to naphthacene (m.p. 337°). The anthracene forms a broad, blue-violet fluorescent zone in the lower part of the column. Continue the development with hexane until fluorescent material commences to pass into the filtrate. Reject the first runnings which contain soluble impurities and yield a paraffin-hte substance upon evaporation. Now elute the column with hexane-benzene (1 1) until the yellow zone reaches the bottom region of the column. Upon concentration of the filtrate, pure anthracene, m.p. 216-216°, which is fluorescent in daylight, is obtained. The experiment may be repeated several times in order to obtain a moderate quantity of material. 

Black, FI.S. (1987). Potential involvement of free radical reactions in ultra violet light-mediated cutaneous damage. Pho-tochem. Photobiol. 46, 213-221. 

Nishi, J., Ogura, R, Sugiyama, M., Hidaka, T. and Kohno, M. (1991). Involvement of active oxygen in lipid peroxide radical reaction of epidermal homogenate following ultra-violet light exposure. J. Invest. Dermatol. 97, 115-119. 

Detection is also frequently a key issue in polymer analysis, so much so that a section below is devoted to detectors. Only two detectors, the ultra-violet-visible spectrophotometer (UV-VIS) and the differential refractive index (DRI), are commonly in use as concentration-sensitive detectors in GPC. Many of the common polymer solvents absorb in the UV, so UV detection is the exception rather than the rule. Refractive index detectors have improved markedly in the last decade, but the limit of detection remains a common problem. Also, it is quite common that one component may have a positive RI response, while a second has a zero or negative response. This can be particularly problematic in co-polymer analysis. Although such problems can often be solved by changing or blending solvents, a third detector, the evaporative light-scattering detector, has found some favor. 

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