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Phenolphthalein's pH sensitivity is exploited in other applications: concrete has naturally high pH due to the calcium hydroxide formed when Portland cement reacts with water. As the concrete reacts with carbon dioxide in the atmosphere, pH decreases to 8.5–9. When a 1% phenolphthalein solution is applied to normal concrete, it turns bright pink.
The phthalide core is found a variety of more complex chemical compounds including dyes (such as phenolphthalein), fungicides (such as tetrachlorophthalide, often referred to simply as "phthalide"), and natural oils (such as butylphthalide).
c 6 h 4 (ch 3) 2 + 7 + 1 / 2 o 2 → c 4 h 2 o 3 + 4 h 2 o + 4 co 2 Phthalic anhydride and maleic anhydride are recovered by distillation by a series of switch condensers . The naphthalene route (the Gibbs phthalic anhydride process or the Gibbs–Wohl naphthalene oxidation reaction) has declined relative to the o -xylene route.
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Its transition range is around pH 9.3–10.5. Below this pH, it is colorless; above, it is blue. The molar extinction coefficient for the blue thymolphthalein dianion is 38,000 M −1 cm −1 at 595 nm. [2]
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Chemical structure of phenolphthalein, a common phthalein dye. Phthalein dyes are a class of dyes mainly used as pH indicators, due to their ability to change colors depending on pH. [1] They are formed by the reaction of phthalic anhydride with various phenols. They are a subclass of triarylmethane dyes. Common phthalein dyes include ...
Some dolls back then cost $1, which is roughly $35 today. Library of Congress - Getty Images. Emigh-Winchell Hardware Company: 1920s.