Coloration in transmission

Many of the thinner platelets are transparent and a rich ruby-red color in transmission. They give a uniaxial negative interference figure. The crystals are too deeply colored for refractive index determination, but the mean value is greater than 2. 

Laminated glass is used for solar control, particularly where a highly reflective surface is not desired and where the laminate contributes other benefits. In these applications, a uniformly pigmented interlayer is obtained from the manufacturer and the laminate can be prepared by the conventional process. Broad ranges of colors and transmission levels are available with shading coefficients as low as 0.41. Pigmented interlayer is considered to be more... 

If an anodically colored electrochromic material (e.g., Ir02) is used as one electrode in the device in Eig. 33.1fi and a cathodically colored (e.g., WO3) is used as the other electrode, a much larger change in transmission per charge supplied can be seen compared to the case when only one electrode is electrochromic. Also, the use of an intercalation material as the counter electrode may be advantageous for the device shown in Eig. 33.1a, as it can minimize undesired reactions on the counter electrode. 

One problem with photochemical treatment is that the method relies on good light transmission into the reaction medium. The slow coating of the transparent walls of the photoreactor vessel with biological or chemical deposits or coloration in the material to be treated causes loss in efficiency. A possible solution to the first of these problems is the use of ultrasound to protect the photoreactor walls against deposition of such materials [39]. Very general claims have been made in the patent literature relating to the possible combined use of photochemistry with sonochem-... 

The method employs the fact that toluene discolors as it dissolves extractable substances in carbon black. " A previously dried sample of carbon black at 125°C is extracted in toluene for 60 seconds, filtered, and its color intensity is measured in a spectrophotometer at 425 nm. The change in transmission of solution of extractables is recorded. 

When measnring transmission for thin samples, for example films, there is a need to ensnre absorption of IR energy is not too strong in any part of the spectrum. For a colorant in a powdered form the traditional way to obtain an infrared spectrum is to dilute the colorant whilst creating a homogenous dispersion either in Nujol (a hquid paraffin) or an alkali-metal hahde (normally potassium bromide). Clearly, it is important that the diluent (e.g. Nujol or KBr) does not have absorption bands in the same region of the spectrum as the sample being analysed. 

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