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Prediction of Ultrasonic Pulse Velocity of Concrete
Published in Sakshi Gupta, Parveen Sihag, Mohindra Singh Thakur, Utku Kose, Applications of Computational Intelligence in Concrete Technology, 2022
Tanvi Singh, Balraj Singh, Sunita Bansal, Khyati Saggu
The natural alkalinity in concrete provides a protective layer against corrosion. Carbon dioxide in the air reacts with the Calcium salts, resulting in reducing the pH of concrete to below 9. The depth of carbonation is determined using phenolphthalein as an indicator. As a pH indicator, for pH above 9, Phenolphthalein changes color from colorless to pink.
Titrimetric Analysis
Published in Pradyot Patnaik, Handbook of Environmental Analysis, 2017
One of the most common acid–base indicators is phenolphthalein. In an aqueous solution of pH less than 8, it is colorless. As the pH approaches 10, the color turns red. Some of the common acid–base indicators are listed in Table 6.2. An acid–base titration may be graphically represented by a titration curve, which is a plot between the change of pH versus the volume of acid or base added, causing such a pH change. Shapes of some of the titration curves are shown in Figures 6.1 through 6.3. Figure 6.1 illustrates the shape of a titration curve for a strong acid and strong base using the same concentrations of acid and base. Such a titration curve would have a long vertical section, typifying a strong acid–strong base titration. Near this vertical section, the addition of a very small amount of titrant causes a very rapid change in the pH. The midpoint of this vertical section is known as the equivalence point, which theoretically should be equal to the end point of the titration. The equivalence point in an acid–base titration involving equal concentrations of a strong acid and a strong base is 7. In other words, a strong acid would completely neutralize an equal volume of strong base of the same strength, or vice versa at pH 7. Figures 6.2 and 6.3 show the titration curves for acids and bases of different strengths. The vertical section is very short in the weak acid–weak base curve.
Microfluidic Contact Lenses for Ocular Diagnostics
Published in Raju Khan, Chetna Dhand, S. K. Sanghi, Shabi Thankaraj Salammal, A. B. P. Mishra, Advanced Microfluidics-Based Point-of-Care Diagnostics, 2022
Antonysamy Dennyson Savariraj, Ammar Ahmed Khan, Mohamed Elsherif, Fahad Alam, Bader AlQattan, Aysha. A. S. J. Alghailani, Ali K. Yetisen, Haider Butt
Tear pH in a healthy person ranges between 6.5 to 7.6 (Abelson et al. 1981) and a deviation from this towards the alkaline window (pH ≈ 8) is an indication of the early stage of rosacea, a chronic dermatosis causing corneal melting and stromal scarring (Abelson et al. 1980, An et al. 2005). Its occurrence in the ocular environment prior to skin will go unnoticed unless the variation in tear pH is detected. A deviation in pH is not only found in rosacea patients (8.0 ± 0.32) but also in cataract patients in pre- (7.26 ± 0.23) and post- (7.50 ± 0.23) operation stages (Thygesen and Jensen 1987). Also tear pH and buffering capacity are the important yardsticks to evaluate the extent of ocular penetration of drugs (Ahmed and Patton 1984) indicative of the pressing need to monitor tear pH. Most techniques used to date involve electrodes (Fischer and Wiederholt 1982), microelectrodes (Carney et al. 1990), glass probes (Abelson et al. 1981), or fluorescent probes (Chen and Maurice, 1990) to be in contact with the cornea which all could cause inconvenience to the patient and lack continuity in monitoring. Benzenedicarboxylic acid (Yetisen et al. 2020) and anthocyanin (Riaz et al. 2019) functionalized CL pH sensors were truly minimally/noninvasive with the ability to continuously monitor pH in a short range (pH 7.0–8.0) (Yetisen et al. 2020) and pH 6.5–7.5 (Riaz et al. 2019)) limiting them from detecting pH beyond this window. At this juncture MCLs with colorimetric sensing units comprising of a methyl red, bromothymol blue, and phenolphthalein to suit a range of pH both in acidic and alkaline windows (Figure 12.5(G)(i), (H)(i)) (Moreddu et al. 2020b) help in close monitoring of tear pH. Methyl red, a carboxylic acid group, and an amine functional group can work in both acid and base media to detect pH in the range of 4.3–6.2. On the contrary, phenolphthalein is colorless in acidic media, and shows a color shift in alkaline media from pink to fuchsia, due to the formation of quinoid-carboxylated structure with the ability to detect pH from 8.2 to 12.0. Bromothymol blue, being a weak acid, exhibits a color shift from yellow to blue in alkaline media due to the formation of triphenylmethane. This pH sensor assay with the combination of methyl red, bromothymol blue, and phenolphthalein show a green color in neutral environments and its color intensity varies based on the pH. The wearer can capture the color change with a smartphone and the RGB values can be analyzed to detect the pH. Green color indicates a healthy eye and yellow color represents mild acidic condition ascribed to changes in tear buffering capacity (Norn 1985) but an alkaline pH exhibited with blue color indicates rosacea disease (Abelson et al. 1980). This sensor has a quick response of 15 s and has a high sensitivity of 12.23 nm/pH unit.
Experimental analysis of rubble stone masonry walls strengthened by transverse confinement under compression and compression-shear loadings
Published in International Journal of Architectural Heritage, 2018
Fernando F. S. Pinho, Válter J. G. Lúcio, Manuel F. C. Baião
The carbonation of the mortar leads to the lowering of its pH. Thus, to achieve the evolution of the carbonation depth (Cd) of the hydrated air-lime hardened mortar, an acid-base indicator was used (in this case an alcoholic solution of phenolphthalein). The alcoholic solution of phenolphthalein remains colorless or neutral–colored in acid solutions, and turns pink or purple in base solutions. The carbonated area of the specimen, Ca (inside the cross-section of the masonry), is calculated by Expression (1):
Use of Ultrafine Mafic Rocks for the Enhancement of Carbonation Reaction in Lime Renders
Published in International Journal of Architectural Heritage, 2020
Loucas Kyriakou, Ioannis Rigopoulos, Ioannis Ioannou
However, it should be highlighted that the phenolphthalein stain test is only a simple empirical method for estimating the progress of carbonation. This is due to the fact that the phenolphthalein indicator changes color over a narrow range of alkaline environments and not sharply at a specific pH (Lawrence 2006).