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Exposure to sunlight

In the absence of catalysts, toluene when treated with chlorine (or bromine) at the boiling point, preferably with exposure to sunlight or other bright light source, undergoes halogenation in the side chain. The entrance of the first chlorine atom, for example, proceeds at a much faster rate than the entrance of the second chlorine atom so that in practice the major portion of the toluene is converted into benzyl chloride before appreciable chlorination of benzyl chloride occurs ... [Pg.534]

A constant force is applied to an ideal elastomer, assumed to be a perfect network. At an initial temperature Tj the length of the sample is Ij. The temperature is raised to Tf and the final length is If. Which is larger Ij or If (remember F is a constant and Tf > Tj) Suppose a wheel were constructed with spokes of this same elastomer. From the viewpoint of an observer, the spokes are heated near the 3 o clock position-say, by exposure to sunlight-while other spokes are shaded. Assuming the torque produced can overcome any friction at the axle, would the observer see the wheel turn clockwise or counterclockwise How would this experiment contrast, in magnitude and direction, with an experiment using metal spokes ... [Pg.193]

Wea.ther lbillty. One of the more destmctive elements is exposure to sunlight specifically, ultraviolet (uv) light. AH sealants are affected by weathering, but there is much difference in the effect of weathering on different sealants. Most sHicones are stable with respect to uv exposure. Urethanes and polysulfides show effects of uv exposure, but can be formulated with uv absorbers to provide reasonable lifetimes in most appHcations. However, there are exceptions in aH classes of sealants and specifiers must be carehil to look for test data that has proven a specific sealant s durabHity. The source of the test data is also important data from an independent testing laboratory is generaHy apt to be more reHable. [Pg.309]

Vitamin D deficiency in animals may be caused by the fact that the vitamin is not available to the hvestock. Modem animal husbandry subjects animals to total confinement with htde or no exposure to sunlight. This mandates that they be given vitamin D-fortified diets. The vitamin is sensitive to oxidation, heat, light, and minerals, and significant losses may occur in the fortified feed unless the product is adequately protected. Mycotoxins in feeds also interfere with utilization of vitamin D in feeds (207—209). [Pg.137]

Pure carbon disulfide is a clear, colorless Hquid with a deHcate etherHke odor. A faint yellow color slowly develops upon exposure to sunlight. Low-grade commercial carbon disulfide may display some color and may have a strong, foul odor because of sulfurous impurities. Carbon disulfide is slightly miscible with water, but it is a good solvent for many organic compounds. Thermodynamic constants (1), vapor pressure (1,2), spectral transmission (3,4), and other properties (1,2,5—7) of carbon disulfide have been deterrnined. Principal properties are Hsted in Table 1. [Pg.26]

Chloroform slowly decomposes on prolonged exposure to sunlight in the presence or absence of air and in the dark in the presence of air. The products of oxidative breakdown include phosgene, hydrogen chloride, chlorine, carbon dioxide, and water. At 290°C, chloroform vapor is not attacked by oxygen. In contact with iron and water hydrogen peroxide is also produced, probably by the following reaction sequence (2) ... [Pg.524]

Although the proposed appHcations for photochromic systems are numerous, few have received broad use. By far, the most successful commercial apphcation is the use of photochromic silver halide-containing glasses in prescription eyewear. The convenience of having lenses that darken automatically upon exposure to sunlight has proven appealing to spectacle wearers (35). With the increasing penetration of plastic lenses into the ophthalmic market, the desire for plastic photochromic ophthalmic lenses has also increased, and considerable effort has been spent on the discovery of photochromic systems for plastic eyewear. [Pg.165]

Desyl chloride (a-cbloro-desoxybenzoin, m-chloro-co-phenyl acetophenone) [447-31-4] M 230.7, m 62-64 , 66-67 ,67.5 , 68 . For the purification of small quantities recrystallise from pet ether (b 40-60°), but use MeOH or EtOH for larger quantities. For the latter solvent, dissolve 12.5g of chloride in 45mL of boiling EtOH (95%), filter and the filtrate yields colourless crystals (7.5g) on cooling. A further crop (0.9g) can be obtained by cooling in an ice-salt bath. It turns brown on exposure to sunlight but it is... [Pg.186]

Because the polybutadiene component is liable to oxidation, ABS materials are embrittled on prolonged exposure to sunlight. By replacing polybutadiene rubber with other elastomers that contain no main chain double bonds it has been possible to produce blends generally similar to ABS but with improved weathering resistance. Three particular types that have achieved commercial status are ... [Pg.449]

The chemical resistance of celluloid is not particularly good. It is affected by acids and alkalis, discolours on exposure to sunlight and tends to harden on aging. More seriously it is extremely inflammable, this being by far the greatest limitation of the material. [Pg.619]

Free radical additions to mono-olefins are quite common and can frequently be employed to advantage on a synthetic scale. Formamide, for example, on exposure to sunlight or UV radiation adds to olefins in an anti-Markovnikov sense giving 1 1 adducts that are readily isolated and crystallized. Moreover, since alkyl formamides may be conveniently converted to carboxylic acids by conventional means, the reaction represents a general method of chain extension. [Pg.141]

Sonnen-. of the sun, sun, solar, helio-. -auge, n. adularia. -bahn, /. ecliptic, -belichtung, /. exposure to sunlight, solar irradiation, insolation. [Pg.414]

These materials are now widely used for coating both steel and concrete surfaces that are subject to a particularly aggressive environment (e.g. North Sea oil platforms). There is less validity for their use under normal atmospheric conditions since they are relatively expensive and tend to chalk on exposure to sunlight. However, their use as zinc phosphate, pretreatment or blast primers for blast-cleaned steel which is subsequently overcoated by any other paint system is an extremely valuable contribution to the painting of new steel work. [Pg.129]

A disadvantage of adsorption indicators is that silver halides are sensitised to the action of light by a layer of adsorbed dyestuff. For this reason, titrations should be carried out with a minimum exposure to sunlight. When using adsorption indicators, only 2 x 10-4 to 3 x 10 3 mol of dye per mol of silver halide is added this small concentration is used so that an appreciable fraction of the added indicator is actually adsorbed on the precipitate. [Pg.347]

Schultz and Ganguly, in 1925, noted that the surface of pulverized TNT became colored on exposure to sunlight. They concluded that tautomeric quinoximes were formed thru an unstable intermediate. In acetone, a stable intermediate formed (Ref 1). Gray, Bonomo and Denner (Ref 8) could not repeat their results Leighton and Lucy studied o-nitrobenzalde-... [Pg.735]

Prolonged exposure to sunlight may result in skin reactions similar to a severe sunburn (photosensitivity reactions). When going outside, cover exposed areas of the skin or apply a protective sunscreen to exposed areas. [Pg.63]

Griseofulvin Beneficial effects may not be noticed for some time tiierefore, take the drug for die full course of dierapy. Avoid exposure to sunlight and sunlamps because an exaggerated skin reaction (which is similar to a severe sunburn) may occur even after a brief exposure to ultraviolet light. [Pg.136]

Doxycycline This drug can cause photosensitivity. Even relatively brief exposure to sunlight may cause sunburn. Avoid exposure to die sun by wearing protective clodiing (eg, long-sleeved shirts and wide-brimmed hats) and by using a sunscreen. [Pg.145]

Clirysiasis may occur, especially on areas exposed to sunlight. Avoid exposure to sunlight or ultraviolet light. [Pg.196]

Avoid prolonged exposure to sunlight or sunlamps because an exaggerated reaction to the ultraviolet light may occur (photosensitivity), resulting in sunburn. [Pg.292]

Thiazide and related diuretics, loop diuretics, potassium-sparing diuretics, carbonic anhydrase inhibitors, triamterene Avoid exposure to sunlight or ultraviolet light (sunlamps, tanning beds) because exposure may cause exaggerated sunburn (photosensitivity reaction). Wear sunscreen and protective clothing until tolerance is determined. [Pg.454]

Skin lighteners, freckle and age spot removers, and other remedies for hyperpigmentation are not actually bleaches like the products listed so far. The active ingredient is hydroquinone, which inhibits melanin formation when applied to the skin. Since the effect is easily reversed by exposure to sunlight or ultraviolet light, a sunscreen is usually included in the formula. [Pg.194]

Figure 7. Ozone, hydroxyl, and hydroperoxyl isopleths calculated using a combined clean/polluted air chemical mechanism. A. [O3] contours, ppb. B. [HO.] contours, 10 molecules cm . C. [H02 ] contours, 10 molecules cm Contours are maximum concentrations achieved in one day exposure to sunlight from starting [NMHC] and [NOJ concentrations on axes. Figure 7. Ozone, hydroxyl, and hydroperoxyl isopleths calculated using a combined clean/polluted air chemical mechanism. A. [O3] contours, ppb. B. [HO.] contours, 10 molecules cm . C. [H02 ] contours, 10 molecules cm Contours are maximum concentrations achieved in one day exposure to sunlight from starting [NMHC] and [NOJ concentrations on axes.
Luminescence measurements on proteins occupy a large part of the biochemical literature. In what surely was one of the earliest scientific reports of protein photoluminescence uncomplicated by concurrent insect or microorganism luminescence, Beccari (64), in 1746, detected a visible blue phosphorescence from chilled hands when they were brought into a dark room after exposure to sunlight. Stokes (10) remarked that the dark (ultraviolet) portion of the solar spectrum was most efficient in generating fluorescent emission and identified fluorescence from animal matter in 1852. In general, intrinsic protein fluorescence predominantly occurs between 300 nm and 400 nm and is very difficult to detect visually. The first... [Pg.9]

The a- and [3-isomers of endosulfan undergo photolysis in laboratory tests after irradiation in polar solvents and upon exposure to sunlight on plant leaves. The a-isomer also undergoes isomerization to the P-isomer, which is relatively more stable (Dureja and Mukerjee 1982). A photolytic half-life of about 7 days was reported for endosulfan by EPA (1982c). The primary photolysis product is endosulfan diol, which is subsequently photodegraded to endosulfan a-hydroxyether. Endosulfan sulfate is stable to direct photolysis at light wavelengths of >300 nm however, the compound reacts with hydroxy radicals, with an estimated atmospheric half-life of 1.23 hours (HSDB 1999). [Pg.228]


See other pages where Exposure to sunlight is mentioned: [Pg.341]    [Pg.486]    [Pg.279]    [Pg.468]    [Pg.229]    [Pg.456]    [Pg.73]    [Pg.403]    [Pg.413]    [Pg.161]    [Pg.321]    [Pg.367]    [Pg.301]    [Pg.438]    [Pg.275]    [Pg.388]    [Pg.129]    [Pg.252]    [Pg.331]    [Pg.781]    [Pg.97]    [Pg.186]    [Pg.58]    [Pg.102]   
See also in sourсe #XX -- [ Pg.15 ]




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