Iodine color scale

Deutsches Institut fiir Normung, Testing of fabric softeners measurement of light transmission with the iodine color scale (in German), DIN 53403. Deutsches Informationszentrum fiir technische Regeln. Berlin Beuth. 

Bromate and iodate salts are prepared on a much smaller scale than chlorates. Under appropriate conditions, these ions undergo oscillating chemical reactions known as chemical clocks. The best known clock reaction is observed when an acidified solution of sodium sulfite (Na2S03) is mixed with an excess of iodate in the presence of starch indicator. After a suitable induction period allowing for sodium sulfite reduction of iodate to iodide [Eq. (44)], the blue, starch-iodine color periodically appears and disappears as the iodide is oxidized to iodine [Eq. (45)], and the iodine is reduced back to iodide [Eq. (46)]. 

Some laboratories measure the absorbance at a specified wavelength using a spectrophotometer and convert the absorbance reading to the iodine or platinum-cobalt color scale using a linear calibration plot. These calibrations are, strictly speaking, only valid when the absorbance spectrum of the colored impurity of interest is exactly the same as that of iodine/iodide or of platinum/cobalt solution. 

The quahty of sulfonic acids produced as iatermediates on an iadustrial scale is important to detergent manufacturers. Parameters such as color, water, free oil (unsulfonated material), and acid value (actual sulfonic acid) are all factors that determine the quaUty of a sulfonic acid. The quaUty of the feedstock prior to sulfonation, such as iodine value, water content, and sulfonatabiUty, affects the quaUty of the sulfonic acid produced. Sulfonation conditions, such as temperature, molar ratio, rate, etc, also affect the quaUty of sulfonic acid. 

During the appropriate tests phthalic anhydride was smoothly esterified with 2-ethylhexanol in the mole ratio 1 4. The reaction temperature rose to 200°C. after about 15 minutes, then rose slowly up to 210°C. till the end of the esterification. Table I shows the esterification time in hours after 99.9% conversion, while continuously removing the reaction water, according to the acid number relative to monooctyl phthalic acid. Furthermore, it indicates the ester colors according to the iodine scale in milligrams iodine/100 ml., whereby 1 mg. iodine/100 ml. can be more or less compared with a dye number of 120 APHA. Since, the values are obtained with the same starting materials, it is possible to compare the color numbers. They show that with the same times, the amphoteric catalysis achieves better colors than in the reaction course containing catalytically effective acids. 

Detector tubes A simple and relatively inexpensive measurement method involves the use of calibrated stain-length detector tubes such as those produced by Draeger, Kitagawa, Gastec, MSA-AUER, and others. CO detector tubes often rely on the reaction of CO with iodine pentoxide, which produces a purple colored iodine stain. The detector tube carries a scale calibrated in parts per million and the length of the color stain that develops after the required number of pump strokes corresponds to the concentration of CO in the sample ... 

This computer-screen image was obtained by a scanning tunneling microscope (discussed in Chapter 7) the color was added to the image by computer. Iodine atoms are the large peaks with pink tops. Note the "vacancy"in the array of iodine atoms. A scale shows the size of the atoms in nanometers. 

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