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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.
A universal indicator is usually composed of water, 1-propanol, phenolphthalein, sodium hydroxide, methyl red, bromothymol blue, sodium bisulfite, and thymol blue. [5] The colours that indicate the pH of a solution, after adding a universal indicator, are:
Ferroxyl indicator, or rust indicator, is a solution containing potassium hexacyanoferrate(III), phenolphthalein and sodium chloride. It turns blue in the presence of Fe 2+ ions, and pink in the presence of hydroxide (OH-) ions. It can be used to detect metal oxidation, and is often used to detect rusting in various situations.
For example, sodium hydroxide, NaOH, is a strong base. NaOH(aq) → Na + (aq) + OH − (aq) Therefore, when a strong acid reacts with a strong base the neutralization reaction can be written as H + + OH − → H 2 O. For example, in the reaction between hydrochloric acid and sodium hydroxide the sodium and chloride ions, Na + and Cl − take ...
For optimal accuracy, the color difference between the two species should be as clear as possible, and the narrower the pH range of the color change the better. In some indicators, such as phenolphthalein, one of the species is colorless, whereas in other indicators, such as methyl red, both species confer a color. While pH indicators work ...
A base was therefore a metal hydroxide such as NaOH or Ca(OH) 2. Such aqueous hydroxide solutions were also described by certain characteristic properties. They are slippery to the touch, can taste bitter [1] and change the color of pH indicators (e.g., turn red litmus paper blue).
Sodium hydroxide, also known as lye and caustic soda, [1] [2] is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations Na + and hydroxide anions OH −. Sodium hydroxide is a highly corrosive base and alkali that decomposes lipids and proteins at ambient temperatures and may cause severe ...
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]