Strong Acid-strong Base Research Articles

An Overview of the Use of Natural Indicators in Acid-Base Titrations

While titrimetric and gravimetric analysis were the most concerning analytical techniques, they are now the most commonly used techniques for identifying chemicals. The endpoint in the titrimetric analysis method is identified by colour changes from one medium to another caused by the addition of chemicals referred to as indicators. There are a lot of synthetic indicators on the market these days, which are expensive and pollute the environment. Human toxicity is produced by a number of synthetic markers. As demonstrated by their use in acid-base titrimetric analysis, floral extracts have a very promising analytical potential. Seven plant extracts were found to function well in strong acid-strong base titrations: violet cabbage, beetroot, red hibiscus flower (shoe flower), turmeric powder, red rose flower, henna leaves, and pink Mirabilis Jalapa flower (4 o'clock flower). For the violet cabbage, there was a noticeable and distinct colour shift from pale pink to violet; for the beetroot, it was dark brown to red; and for the red hibiscus flower extract, it was pale yellow to pink.

EXTRACTION AND CHARACTERIZATION OF CURCUMIN FROM TURMERIC RHIZOMES GROWN IN MÉRIDA, VENEZUELA

The extraction of naturally occurring compounds is one of the fastest-growing industries because of its benefits against its synthetic analogs. Environmental protection must require the use of natural products instead of chemicals to minimize pollution. Thus, this investigation studies the use of some natural product, as curcumin, as naturally occurring acid‐base indicators. Curcumin can be used as acid-base indicators since it was found that it possesses pH-dependent solubility. Curcumin, the major active component of turmeric, Curcuma longa (Zingiberaceae), is used as a spice in curry and as a coloring agent in yellow mustards, cosmetics, pharmaceuticals, and hair dyes. In this research, the main compound colored rhizome of turmeric (Curcuma longa) cultivated in Mérida, Venezuela, is extracted: Curcumin (C21H20O6) (1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, in a yield of 3.42% after 8 hours of extraction using soxhlet extractor system with organic solvents (hexane and ethanol). The thin-layer chromatography and column performed separation and purification using a mobile phase, a mixture of chloroform-hexane 3:2. The dye was characterized by spectroscopic analysis of visible ultraviolet (UV-Vis) and infrared (IR), in addition to his studio in steering sensitivity as an acid-base indicator. This dye is useful as an acid-base indicator in strong acid-strong base volumes and did not require large amounts of it as it has high sensitivity. The results indicate that curcumin as an acid-base indicator allows the development of new standards in different chemistry fields that require this type of analysis.

GREEN CHEMISTRY: ROSELLE’S COROLLA EXTRACT AS A SUBSTITUTE FOR HAZARDOUS INTERNAL INDICATORS IN VOLUMETRIC ANALYSIS

Indicators used in acid-base titration show well marked changes of colour in certain intervals of pH. Most of these indicators are organic dyes and are of synthetic origin. Today synthetic indicators are the choice of neutralization titrations. But due to environmental pollution, availability and cost, the search for natural compounds as an acid-base indicator was started. The present work highlights the use of the ethanolic extract of the corolla of Roselle (Hibiscus sabdariffa) as a pH indicator in strong acid-strong base, strong acid weak base, weak acid strong base and weak acid-weak base titrations. This natural indicator is easy to extract as well as easily available. The results showed that the Roselle’s corolla indicator gave red color in acidic solution, while green in basic solution. The comparison indicators used in this research were phenolphthalein, methyl red and phenol red. Hopeful results were obtained when it was compared against standard synthetic indicators. The equivalence points obtained match with the equivalence points obtained by standard indicators. Therefore this natural indicator is found to be useful, economical, simple, precise and eco-friendly for acid base titration.

Natural Plant Extracts as Acid-Base Indicator and Determination of Their pKa Value

Commonly used indicators for acid-base titrations are synthetic, and this work was focused to identify the eco-friendly natural indicators and to determine their pKa values. The analytical potential of the flower extracts is very promising as seen in its application in acid-base titrimetry. These selected flower extracts were found to perform well in titrating strong acid-strong base than in weak acid-strong base. We have obtained a sharp and clear colour change from red to brownish yellow for the Bougainvillea glabra extract, from red to yellow for the Bauhinia purpurea extract, and from red to brownish yellow for the Impatiens balsamina extract. All the three flower extracts gave clear colour change with acids and bases, and the colour change was maintained with different acids and bases. The sharp contrast between their colours in acid and base made the pigment suitable for use as acid-base indicators. As these flower extracts have very simple,cost-effective, environment friendly extraction procedure and excellent performance with sharp colour change in end points of the titrations, it would be possible to replace the standard indicators being used in conventional laboratories with natural flower indicators.

ETHANOLIC EXTRACT OF ARISTOLOCHIA BRACTEOLATA FLOWER AS A NATURAL INDICATOR FOR ACID-BASE TITRATION

In acid-base titration or acid-base neutralization reaction the change in color due to change pH of the solution is caused due to a third substance which is termed as acid-base indicator or pH indicator. Every indicator shows different range of colors at different pH ranges. Synthetic indicators have been widely employed as indicators in acid-base titrations; however, due to environmental pollution, availability and cost, natural compounds are best alternates. Natural pigments in plants are highly colored substances and may show sharp color changes with variation in pH. In the present study an attempt has been made to extract natural indicator from flower of Aristolochia bracteolate. The equivalence points of the titrations namely strong acid-strong base, strong acid-weak base, weak acid-strong base and weak acid weak base titrations, using flower extract of A. bracteolate were coincident with the equivalence points obtained by the synthetic indicator phenolpthalein. From the results of the study, it may be concluded that ethanolic extract of A. bracteolate flower as an indicator for acid-base titration could be effectively employed as a substitute to the synthetic acid-base indicators.

APPLICATION OF FLOWER COLOR VARIATIONS TO Impatiens balsamina L. AS AN ENVIRONMENTALLY FRIENDLY ACID-BASE INDICATOR

An acid-base titration is one of the quantitative analysis methods involving a high-polluting, harmful, hazardous, and relatively expensive synthetic indicator. The development of the concept of green chemistry encourages research to invent natural indicators that are more environmentally friendly. Impatiens balsamina L. flower has a variety of colors and contains anthocyanin pigments. Rose pink, red, violet, orangish red, and pink Impatiens balsamina L. flower were extracted with acidified ethanol solvent. All five I. balsamina L. flower extracts indicate discoloration on pH range 10-12. Violet flower extract has an error percentage of strong acid-strong base titration which was 50.48 ± 2.18%, while in strong acid-weak base titration was 19.27 ± 1.15%. Meanwhile, it cannot be applied in weak acids-strong base titration. Thus, I. balsamina L. flowers can be used as an alternative to environment-friendly natural acid-base indicators.

Bauhinia racemosa as Natural pH Indicator

The substance which causes change in colour with respect to change in pH of solution is termed as acid-base indicator. At different pH range every indicator shows different range of colors. There are numbers of chemical or synthetic indicators which are used in acid-base titration but these are slight costlier and not available easily every time hence natural indicator i.e. obtained from plant source are come forth, because plants easily available everywhere extraction process is less expensive. We use Bauhinia racemosa flower extract and Methyl red as indicators in titration s of strong acid-strong base (HCl and NaOH), strong acid-weak base (HCl and NH3), and weak acid-strong base (CH3COOH and NaOH) and weak acid-weak base (CH3COOH and NH3). The result obtained from titration of natural indicator (i.e. Bauhinia racemosa) are near to the result obtained from titration of standard indicator (i.e. Methyl red) in this research work we successfully prove that natural indicator can also used in titration.

Acid···Amide Supramolecular Synthon in Cocrystals: From Spectroscopic Detection to Property Engineering.

The acid···amide dimer heterosynthon in cocrystals of aromatic acids and primary amides is identified by marker peaks in the IR spectra that are characteristic of individual N-H···O and O-H···O interactions and also of the extended synthon. The O-H···O hydrogen bond is crucial to heterodimer formation in contrast to the N-H···O bond. A combinatorial study, tuning the chemical nature of acid and amide functionalities, leads to 22 cocrystals out of 36 crystallization attempts. Four quadrants I-IV are defined based on acidity and basicity of the acid and amide components. The strong acid-strong base combination in quadrant I favors the planar acid···amide heterodimer in its eight cocrystals. Quadrant IV with its weak acid-weak base combination is the least favored for the planar heterosynthon and synthon diversity is observed in the eight cocrystals obtained. The strong-weak and weak-strong combinations in quadrants II and III are expectedly ambivalent. This exercise highlights the effect of molecular features on supramolecular behavior. Quadrant I crystals, with their propensity for the planar acid···amide heterodimer are suitable for the engineering of crystals that can be sheared. This quadrant favors the formation of elastic crystals too. The overall result is that 57% (4 in 7) of all crystals in this quadrant are deformable, compared with 14% (1 in 7) in the three other quadrants. This work is a complete crystal engineering exercise from synthon identification to a particular desired crystal packing to property selection. One can virtually anticipate the mechanical property of a putative acid···amide cocrystal from a knowledge of just the molecular structures of the constituent acid and amide molecules.

Passiflora incarnate as Natural pH Indicator

The substance which causes change in colour with respect to change in pH of solution is termed as acid-base indicator. At different pH range every indicator shows different range of colors. There are numbers of chemical or synthetic indicators which are used in acid-base titration but these are slight costlier and not available easily every time hence natural indicator i.e. obtained from plant source are come forth, because plants easily available everywhere extraction process is less expensive. We use Passionflower and phenolphthalein as indicators in titration s of strong acid-strong base (HCl and NaOH), strong acid–weak base (HCl and NH3), and weak acid-strong base (CH3COOH and NaOH) and weak acid-weak base (CH3COOH and NH3). The result obtained from titration of natural indicator (i.e. passionflower extract) are near to the result obtained from titration of standard indicator(i.e. phenolphthalein).in this research work we successfully prove that natural indicator can also used in titration.

Optical ph sensing material prepared from doped sol-gel film for use in acid-base titration

An optical pH sensing material has been prepared in this study by using sol-gel technique. Bromothymol blue, bromophenol blue and thymol blue were chosen in this study as acidbase indicators for strong acid-strong base, strong acid-weak base and weak acid-strong base titration, respectively. The results show that these indicators could be successfully entrapped inside the sol-gel film and still maintain its chemical behaviour as in solution. The entrapped acid-base indicators respond well to any pH changes and could be used to determine the end-point of the acid-base titration.

Natural Dyes as Acid-Base Indicators fromBeta vulgaris

In acid-base titrations, indicator are used to show a sharp color changes at end point which are mostly organic dyes. Due to environmental pollution, availability and cost, the search for natural acid-base indicator was started. In the present study the extract of Beta vulgaris was used to replace the synthetic indicators due to the disadvantage of less availability and high cost of synthetic dye. Extract of Beta vulgaris gives sharp and intense color changes as compared to synthetic indicator. The extracts were evaluated by using strong acid-strong base, strong acid-weak base, weak acid-strong base and weak acid-weak base. In all these titrations the extract was found to be very useful and accurate for indicating the neutralization point. Methanolic extract of Beta vulgaris was found to be a very useful, economical, simple and accurate for titration. The proposed herbal indicators can be used as a substitute to synthetic indicators.

A Comparative Study of Applying Active-Set and Interior Point Methods in MPC for Controlling Nonlinear pH Process

A comparative study of Model Predictive Control (MPC) using active-set method and interior point methods is proposed as a control technique for highly non-linear pH process. The process is a strong acid-strong base system. A strong acid of hydrochloric acid (HCl) and a strong base of sodium hydroxide (NaOH) with the presence of buffer solution sodium bicarbonate (NaHCO3) are used in a neutralization process flowing into reactor. The non-linear pH neutralization model governed in this process is presented by multi-linear models. Performance of both controllers is studied by evaluating its ability of set-point tracking and disturbance-rejection. Besides, the optimization time is compared between these two methods; both MPC shows the similar performance with no overshoot, offset, and oscillation. However, the conventional active-set method gives a shorter control action time for small scale optimization problem compared to MPC using IPM method for pH control.

Boerhavia Erecta Linn. Stem Bark Extract A Natural Acid-Base Indicator

Synthetic indicators have been tried as indicators in acid-base titrations but due to environmental pollution, availability and cost, natural compounds are best alternate. Natural pigments in plants are highly colored substances and may show sharp color changes with variation in pH .An attempt has been made to extract natural indicator by maceration from stem bark of Boerhavia erecta Linn. The equivalence points obtained by the BEI strong acid-strong base, strong acid-weak base, weak acid-strong base and weak acid weak base titrations were coincident with the equivalence points obtained by synthetic indicators. Thus natural indicator was found to be eco-friendly, economical, simple and accurate for all acid-base titrations. Phytochemical analysis and spectral studies confirmed presence of anthocyanins and flavonoids in BEI responsible for accurate and sharp colour change at equivalence point. The present study reports the use of this natural indicator in different acid base titrations.

An Alternative to Synthetic Acid Base Indicator-Tagetes Erecta Linn

The present work highlights the use of the methanolic extract of the flowers of Tagetes erecta as an acid-base indicator in acid-base titrations. This natural indicator is easy to extract as well as easily available. Indicators used in titration show well marked changes of colour in certain intervals of pH. Most of these indicators are organic dyes and are of synthetic origin. Today synthetic indicators are the choice of acid-base titrations. But due to environmental pollution, availability and cost, the search for natural compounds as an acid-base indicator was started. Herbal indicators are evaluated by using strong acid-strong base, strong acid-weak base, weak acid-strong base and weak acid weak base. In all these titrations the methanolic extract of the flowers of Tagetes erecta was found to be very useful, economical, simple and accurate for acid base titration.

Low-Cost Laboratory Data Acquisition System Based on the Z8 ENCORE!â„¢ Microcontroller for pH Measurement

A pH measurement-auto-titration data acquisition system based on the Z8 Encore!™ Z8F6401 Flash microcontroller was devised with a glass electrode acting as a pH sensor. The data acquisition system allows buffer calibration, pH measurement of samples and the option to perform an automated strong acid-strong base titration via a solenoid pinch valve which actuates the flow of titrant. The results given by the pH measurement system were comparable to that of Sartorius® PB-20 pH meter using t-Test within the pH range 4.00 to 10.00. This can be attributed to the very linear response of the sigma-delta analog-to-digital converter (ADC) of the Z8F6401 to changes in potential. The auto-titration setup gave an accurate titrant volume delivery to the bromothymol blue endpoint (pH 6.2 to 7.6) for a strong acid-strong base titration.

Electrolyte diodes with weak acids and bases. I. Theory and an approximate analytical solution

Until now acid-base diodes and transistors applied strong mineral acids and bases exclusively. In this work properties of electrolyte diodes with weak electrolytes are studied and compared with those of diodes with strong ones to show the advantages of weak acids and bases in these applications. The theoretical model is a one dimensional piece of gel containing fixed ionizable groups and connecting reservoirs of an acid and a base. The electric current flowing through the gel is measured as a function of the applied voltage. The steady-state current-voltage characteristic (CVC) of such a gel looks like that of a diode under these conditions. Results of our theoretical, numerical, and experimental investigations are reported in two parts. In this first, theoretical part governing equations necessary to calculate the steady-state CVC of a reverse-biased electrolyte diode are presented together with an approximate analytical solution of this reaction-diffusion-ionic migration problem. The applied approximations are quasielectroneutrality and quasiequilibrium. It is shown that the gel can be divided into an alkaline and an acidic zone separated by a middle weakly acidic region. As a further approximation it is assumed that the ionization of the fixed acidic groups is complete in the alkaline zone and that it is completely suppressed in the acidic one. The general solution given here describes the CVC and the potential and ionic concentration profiles of diodes applying either strong or weak electrolytes. It is proven that previous formulas valid for a strong acid-strong base diode can be regarded as a special case of the more general formulas presented here.

PH Process Control with Fictitious Smoothing Tanks

AbstractThis paper is concerned with pH process control based on sensitivity analysis, applied to a strong acid‐strong base system. The models were developed, using the concept of chemical reaction invariants. Derived from GMC synthesis, a non‐linear PI control law was presented and the results compared to the classical PI controller. The presence of uncertainties or a shift in the system's behavior has been considered, either on steady state or from the dynamic point of view. The analysis showed that sensitivity presents the same behavior in both cases, thus demonstrating the feasibility of the application with the non‐linear PI controller. The results of sensitivity analysis indicate a strategy for improving control structure performance, using the concept of fictitious smoothing tanks, inserted into computer codes for process control, yet without incurring appreciable computational load or additional costs.

Acid-Base Indicators: A New Look at an Old Topic

An introductory acid-base experiment for use in general chemistry is described. The students are asked to evaluate four indicators for a strong acid-strong base titration using dilute solutions of each. A conductivity probe is utilized to monitor the progress of the titration. By correlating the color changes for each indicator with the conductivity minimum, the indicators are evaluated for their suitability under the given conditions. After choosing the best indicator of the group, the same solution of standard base is used to titrate an unknown acid quantitatively using only the color change to gauge the volumetric endpoint.

LAS ANTOCIANIDINAS COMO INDICADORES: UNA EXPERIENCIA DE APRENDIZAJE ALREDEDOR DEL PROCESO DE NEUTRALIZACIÓN

A man is in the center of an ecosystem, everything that rounds him is potentially usefull. Man uses plants as a natural resource for survival as well as for learning ofscientific concepts, among others. ln the current work antocianidines present in summerflowers (Bouganviliea Glabra) and egg plant peels (Solanum Melongena) were used aspH indicators for strong acid-strong base neutralization reactions, replacing bromotimol.As an alternative for the work, students were involved in an active and participatingprocess for solving problems through research based on F Coit Butler’s model, DavidAusubel’s fundamental principle on educational psychology and research activities.The methodology used includes performing a pre-test to determine the students’knowledge level, followed by four learning activities that Iead to the solution, throughresearch, of a real life problem, the concept normality concept, the plants activeprinciples isolation such as the antocianidines, ant the neutralization concept.

GLEE, a new computer program for glass electrode calibration

A new computer program (GLEE, glass electrode evaluation) has been written for the calibration of a glass electrode by means of a strong acid-strong base titration. This program provides an estimate of the carbonate contamination of the base, the pseudo-Nernstian standard potential and slope of the electrode and, optionally, the concentration of the base and pK(W.) The program runs under the Windows 3.1x, 9x and NT operating systems.