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Phenolphthalein is slightly soluble in water and usually is dissolved in alcohols in experiments. It is a weak acid, which can lose H + ions in solution. The nonionized phenolphthalein molecule is colorless and the double deprotonated phenolphthalein ion is fuchsia. Further proton loss in higher pH occurs slowly and leads to a colorless form.
Upon reduction, the very intense pink color of the cationic form of phenolphthalein fades to a faint yellow color. It is this form of phenolphthalein that is present in Kastle–Meyer test kits. In order to generate the intense pink color indicative of a positive test, the reduced phenolphthalein must be oxidized back to its normal, colored form.
Phenol red exists as a red crystal that is stable in air. Its solubility is 0.77 grams per liter (g/L) in water and 2.9 g/L in ethanol. [1] It is a weak acid with pK a = 8.00 at 20 °C (68 °F). A solution of phenol red is used as a pH indicator, often in cell culture.
A liquid fat sample combined with neutralized 95% ethanol is titrated with standardized sodium hydroxide of 0.1 eq/L normality to a phenolphthalein endpoint. The volume and normality of the sodium hydroxide are used, along with the weight of the sample, to calculate the free fatty acid value. [3]
[5] [6] An increase of alcohol intake by ~20 g ethanol/day will raise the PEth 16:0/18:1 concentration by ~0.10 μmol/L, and vice versa if the alcohol consumption has decreased. However, it has been demonstrated that there can be significant inter-personal variation, leading to potential misclassification between moderate and heavy drinkers. [ 7 ]
Solution: The main components of a universal indicator, in the form of a solution, are thymol blue, methyl red, bromothymol blue, and phenolphthalein. This mixture is important because each component loses or gains protons depending upon the acidity or alkalinity of the solution being tested. It is beneficial to use this type of universal ...
Phenolphthalein can be synthesized by the condensation of phthalic anhydride with two equivalents of phenol under acidic conditions (hence the name). It was discovered in 1871 by Adolf von Baeyer. [8] [9] [10] Synthesis of phenolphthalein [11]
A precipitate should form and be vacuum filtered to obtain a solid. It should then be washed with water and dried, yielding a yellow product. It should then be recrystallized from glacial acetic acid to yield yellow needles. The product is BNMP. The reaction can go further by combining 15.5 g of BNMP with 0.18 g 10% Pd/C and 50 mL ethanol.