Quantitative Use of Red Cabbage To Measure pH through Spectrophotometry: A Laboratory Experience for General Chemistry Students

Cannon, Mark B.; Ong, Kai Li

doi:10.1021/bk-2013-1130.ch010

Cited by 4 publications

(6 citation statements)

References 16 publications

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“…Figure summarizes the chemical structure and acid–base equilibria of these compounds. Curcumin has p K a values of 7.8, 8.5, and 9.0 for its three acidic protons and turns from red at pH 8.6 to yellow at pH 7.4; , while anthocyanin from CAB presents a full color palette, from yellow at pH 13.0 to pink below pH 5.0, with several p K a values. − …”

Section: Designing the Experimentsmentioning

confidence: 99%

Turmeric and RGB Analysis: A Low-Cost Experiment for Teaching Acid–Base Equilibria at Home

et al. 2021

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An experimental approach to chemistry is a more meaningful way to learn than the use of textbooks alone. Working in the laboratory helps students understand basic concepts through their active engagement. Here, we present a series of inexpensive and environmentally friendly laboratory exercises on acid–base equilibrium. Their difficulty level is low, and they can be performed at home. Thus, they are especially suited for teaching in a social-distance context, such as during the COVID-19 pandemic. The experiments were designed to exemplify the main concepts of acid–base equilibrium, buffer capacity, and titration curves, using safe household reactants and no special equipment. RGB image analysis is used to detect pH variation and follow experiments’ progress. Titration of sodium carbonate with acetic acid using curcumin and red cabbage extracts as indicators is described. Our results show that curcumin extract is an excellent indicator for this purpose, and the end point is clearly observed through image analysis. These assays can be used and further adapted to teach students of different ages and socioeconomic backgrounds.

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Section: Designing the Experimentsmentioning

confidence: 99%

Turmeric and RGB Analysis: A Low-Cost Experiment for Teaching Acid–Base Equilibria at Home

et al. 2021

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“…The absorbance value correlates with the color intensity of the dye solution. Therefore, the Red Cabbage solution at a strongly acidic condition presents a higher intense color (Cannon and Ong, 2013). The related color changes to the pH value can explain by Brouillard mechanism (Brouillard and Dubois, 1977).…”

Section: Resultsmentioning

confidence: 99%

“…The related color changes to the pH value can explain by Brouillard mechanism (Brouillard and Dubois, 1977). In a strongly acidic condition (pH ≤ 3), anthocyanins exist only as flavylium cations (red color) (Cannon and Ong, 2013) and the cationic form of the molecule predominates [orange or red, Figure 2(a)]. The color intensity of the dye solution becomes down at the mildly acidic conditions (4 ≤ pH ≤ 5), which is providing a colorless carbinol pseudo-base.…”

Section: Resultsmentioning

confidence: 99%

Red cabbage anthocyanins content as a natural colorant for obtaining different color on wool fibers

Barani

Maleki

2020

PRT

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Purpose Finding blue colorants from natural sources is extremely difficult and, usually, the anthocyanin compounds are used for producing the blue color. This study aims to apply the Red Cabbage as a natural colorant to obtain different colors on wool yarn, as well as specify the optimum dyeing condition by response surface methodology for obtaining a blue color. Design/methodology/approach The effect of dyeing process parameters such as mordant concentration, dyeing time, pH of dyeing bath and dyeing temperature examined in the color characteristics of the dyed wool samples. Findings The obtained results indicated that the diverse colors achieve by varying the dyeing process parameters, which is in the range of 26° up to 271°. The non-mordanted dyed wool samples showed a red and red brownish color (Hue angle = 26° up to 70°), and the mordanted dyed wool samples showed a blue and blue-greenish color (Hue angle = 230° up to 271°). The obtained blue color with the optimized dyeing condition presented a considerable good wash and lightfastness. Originality/value This study provides a promising application of Red Cabbage as a natural colorant for obtaining different colors by varying the dyeing process parameters such as pH and stannous ion concentrations. The stannous ions yielded a co-pigmentation and presented a blue color on wool fibers, which is extremely difficult to obtain with natural colorant.

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“…In particular, team B, who was in charge of the colorimetric analysis, had the most challenging assignment of all three teams, because unlike the cabbage indicator or the reaction between vinegar and baking soda, there was little to no available information on how to carry out the RGB analysis needed. Team B found ref , but they had to adapt a procedure that was designed for spectrophotometry to work as a colorimetric analysis, and because of this team C required more guidance and input from the instructor, who worked closely with the team over Slack and videos. The truth is the instructor himself did not know prior to phase I exactly how the colorimetric analysis would work, only that in principle it should.…”

Section: Logistics Of the Experimentsmentioning

confidence: 99%

Experimenting with At-Home General Chemistry Laboratories During the COVID-19 Pandemic

et al. 2020

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During the COVID-19 pandemic, an at-home laboratory program was created and implemented for a section of the general chemistry course at the University of Southern California. The experiments were designed to only utilize safe household items and no special equipment. These laboratory activities, spanning over 4 weeks, focused on concepts usually covered in the final one-third of our second-semester chemistry laboratory, including pH, acid−base titrations, buffers, solubility, phase equilibria, and thermodynamics. In this article, we describe the design of the laboratories and our experience with this experiment, while also providing an assessment on how similar activities could be integrated profitably into a regular general chemistry course.

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Quantitative Use of Red Cabbage To Measure pH through Spectrophotometry: A Laboratory Experience for General Chemistry Students

Cited by 4 publications

References 16 publications

Turmeric and RGB Analysis: A Low-Cost Experiment for Teaching Acid–Base Equilibria at Home

Turmeric and RGB Analysis: A Low-Cost Experiment for Teaching Acid–Base Equilibria at Home

Red cabbage anthocyanins content as a natural colorant for obtaining different color on wool fibers

Experimenting with At-Home General Chemistry Laboratories During the COVID-19 Pandemic

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