Carbon-arc lamp

Dichromated Resists. The first compositions widely used as photoresists combine a photosensitive dichromate salt (usually ammonium dichromate) with a water-soluble polymer of biologic origin such as gelatin, egg albumin (proteins), or gum arabic (a starch). Later, synthetic polymers such as poly(vinyl alcohol) also were used (11,12). Irradiation with uv light (X in the range of 360—380 nm using, for example, a carbon arc lamp) leads to photoinitiated oxidation of the polymer and reduction of dichromate to Ct(III). The photoinduced chemistry renders exposed areas insoluble in aqueous developing solutions. The photochemical mechanism of dichromate sensitization of PVA (summarized in Fig. 3) has been studied in detail (13). 

Carbon arc lamps were first developed in the 1840s, and sometimes elaborate towers were created to provide illumination to streets in a few European... 

ISO 4892-4, Plastics - Methods of exposure to laboratory light sources - Part 4 Open-flame carbon-arc lamps, 1994. 

Ytterbium oxide (Yb O ) is used to make special alloys, ceramics, and glass. It can be used for carbon arc-lamp electrodes that produce a very bright light. 

Mean refractive index. bFor carbon arc lamps. Formula is [AlSi04]6(S04)(S,Cl)2(Na,Ca)8. 

Colorfastness to Light. Specimens were exposed to continuous light provided by the carbon arc lamp of a Weatherometer for various periods of time, ranging from 30 min to 40 h. It was necessary to evaluate the color change at more frequent intervals than those suggested in the test method 16A-1977, because studies have indicated silks sometimes lose color within an hour of exposure (7). 

In 1808, Davy invented the carbon arc lamp. He had proposed using carbon as the electrode material instead of metal. (Electrodes are conductors used to establish electrical contact with a nonmetallic part of a circuit.) With carbon electrodes, he made a strong electric current leap from one electrode to the other. This created an intense white light. Davy s invention marked the beginning of the era of electric light. Arc lamps are still used today. 

Carbon arc lamp A lamp for producing very bright white light. 

One of the most important uses of lanthanum compounds is in carbon arc lamps. In a carbon arc lamp, an electrical current is passed through the lamp electrode. The electrode is made of carbon and traces of other materials that have been added. The current causes the carbon to heat up and give off a brilliant white light. The exact color of the light depends on the other materials that have been added to the carbon. Lanthanum fluoride (Laf3) and lanthanum oxide (La203) are usually used for this purpose. 

A related use of praseodymium is in carbon arc lamps, like those used in the motion picture industry. When an electric current is passed through a carbon arc, the arc gives off a brilliant white light. The addition of a small amount of praseodymium gives a brilliant yellow cast to the light. 

A little another character of curves run is observed during irradiation by combined light of mercury-quartz and carbon-arc lamps. During irradiation of the initial CA, as in the previous case, linear dependence of acetic acid accumulation (Figure 2.22, curve 1) is observed. However, induction period is being observed after introduction of azomethines BA and XXXV (Figure 2.22, curves 2 and 3) at the initial phase of irradiation. 

Figure 2.21. Change of the rate of acetic acid accumulation in the process of irradiation by carbon-arc lamp. 1 - CA-film without additive 2 - CA-film -H 2% XXXV.

Ca-stearate (HALS-III, without AO-II). Test specimens compression-molded plates (2.0 mm thick). Weathering test sunshine carbon arc lamp weather meter (WEL-SUN-HC, Suga Test Instruments Co., Ltd.). Black panel temperature 63 3 C, without water spray. Failure criterion time to 507, loss of original elongation (half life time = H.L.T.). IF = H.L.T. with stabilizer/H.L.T. without stabilizer. (b) Test specimens compression-molded sheets (0.5 mm thick). Aging test forced air circulation oven at 150 C. 

Early accelerated weathering apparatus utilized carbon arc lamps with various filters to generate a spectrum that reproduced some of the harmful effects of sunlight. Improved versions of these are still in use and are specified for certain applications. However, many users and specifiers have turned to xenon arc lamp-based machines as these produce a spectrum that more closely matches that of sunlight (Fig. 6.1). Additionally, they are generally less expensive to purchase and to run than the carbon arc machines. Both types nowadays have facilities for the provision of controlled humidity, water spray, periodic water immersion and/or variable temperature cycles. 

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