The Ph Reading of a Glass of Liquid Is Given. Find the Hydrogen Ion Concentration of the Liquid.

Hydrogen Ion Concentration

The estimated hydrogen ion concentration and reaction enthalpies are combined with dynamic temperature profile and kinetic reaction models for estimation of the main quality parameters for dissolving pulp, namely the lignin content and the content and degree of polymerization of the alpha-cellulose fraction.

From: Reckoner Aided Chemical Engineering , 2018

Edible and Nonedible Biodiesel Feedstocks

A.East. Atabani , ... S. Shobana , in Make clean Energy for Sustainable Evolution, 2017

17.16.1 Hydrogen Ion Concentration

Hydrogen ion concentration (the pH) is 1 of the important factors that affect growth and multiplication of algae and hence the oil and biodiesel product. Most algal growth occurs in the region of neutral pH, although optimum pH is the pH of initial civilization in which an alga is adjusted to grow [145]. Bartley et al. [146] found that pH of around viii seems near beneficial for maximum growth charge per unit and lipid accumulation of Nannochloropsis salina and to minimize invading organisms. However, adding buffers will not be cost-effective or realistic at a large scale. They too demonstrated that college pH values per se do not slow Nannochloropsis production. Thus, the addition of CO₂ at large scales is generally valuable for providing an inorganic carbon source for algae.

Moheimani [147] plant pH 7 and 7.5 to be ideal for lipid accumulation in Tetraselmis suecica and Chlorella sp. While, Bartley et al. [146] found no significant outcome of pH change on lipid accumulation, the treatment with a pH alter to 8 exhibited the greatest overall accumulation (averaging 24.75% by mass) of Northward. salina. Rodolfi et al. [148] establish the lipid content (% biomass) for different Nannochloropsis spp. to exist 24.four–35.7%. The earlier results indicate that pH may not exist an important stress factor that triggers increased lipid aggregating in microalgae. Acidic pH of culture media can change nutrient uptake or induce metal toxicity and therefore have an result on algal growth and oil production [149]. The green microalga Chlamydomonas acidophila and the diatom Pinnularia braunii accumulate storage lipids, such as triacylglycerides, nether extremely acidic surroundings (pH i) [150]. However, bones pH decreases membrane-associated polar lipids due to cell bicycle inhibition. In basic pH weather, membrane lipids in Chlorella were observed to be less unsaturated [151].

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Healing and monitoring of chronic wounds: advances in article of clothing technologies

Ensieh S. Hosseini , ... Ravinder Dahiya , in Digital Health, 2021

6.5.2.1 Chemical biosensors

Hydrogen ion concentration is a critical biomarker to determine the wound status. For healthy skin, the pH value is approximately in the range of 5.5 simply for infected wounds, the pH value is in the range of 7-8.5. The alkaline metal nature of pH in the wound is due to the presence of bacterial colonies and enzymes. When a wound is kept in an acidic condition, the fibroblasts proliferate more actively and the wound healing process is stimulated more while an infected wound shows a slightly basic pH surround due to certain enzyme activities, bacterial colonization, and germination of protein structures [83]. Despite the conflicting information on wound pH, the pH has been identified every bit a pregnant parameter in determining the phase of the healing procedure and bacterial colonization [84]. Consequently, several research groups have developed dressings which incorporate pH-sensitive materials. For case, a hydrogel-based wireless pH sensor embedded into a wound dressing has been reported to continuously monitor pH [85]. The device consists of a pH-sensitive polyvinyl alcohol-polyacrylic acid hydrogel placed between ii planar screw coils that human action every bit an inductive transducer (Fig. 6.6A). As pH changes, the hydrogel swells and deswells and the distance separating the ii planar coils alter which results in a change of inductance of the coil and the frequency response of the transducer. Information technology was observed that a linear inductance responds, over the pH ranging from 2 to vii, with a change in the coil separation distance. A network-spectrum analyzer was also used with an antenna to let for wireless measurement of the curlicue gap, and hence pH value. Besides a potentiometric pH sensor embedded on a commercial adhesive bandage has been reported for wound pH monitoring [81]. In this case, the silver/silver chloride (Ag/AgCl) and carbon electrodes accept been screen-printed onto the bandage. The Ag/AgCl reference electrode has been partially coated with a polyvinyl butyral polymer (PVB) whereas the carbon electrode serves equally a working electrode and has been electropolymerized with polyaniline (PANi). Fig. 6.6B shows the fabrication procedure of the printed potentiometric sensor on an adhesive bandage. This wear pH sensor showed a response in a express pH range of 5.5-8 and relatively long-time intervals (upwards to 100   minutes) for the detection of pH fluctuations at a wound site (Fig. 6.6B). The pH bandage sensor exhibited the pH sensitivity shut to the theoretical Nernstian response (59.2   mV/pH) (Fig. 6.6B) in the pH range 4.35-8. Further, less interference to other ions was observerd along with fast response time, good repeatability, reproducibility, and lack of hysteresis issue. This sensor also shows a minimal impact on the sensing operation during different angle cycles. Due to its similarity in the chemical environment in the vicinity of a wound, the sensor could also detect application in human serum [81].

Figure half dozen.6. Example of bandages with integrated pH, temperature, and oxygen sensors. (A) Pattern of a pH-sensitive gel sandwiched between ii inductance coils for continuous wireless pH monitoring and its potential application on wound dressing. Reproduced with permission from ref [85].Copyright 2009 Elsevier. (B) (left) Fabrication of the screen-printed potentiometric electrodes and create a pH-sensitive bandage, (right) Potentiometric fourth dimension-trace of the pH cast sensor from pH eight.51 to 2.69. Reproduced with permission from ref [81]. Copyright 2014 John Wiley and Sons. (C) The smart bandage blueprint with the dispensable part (sensors) and a reusable part (wireless electronics) with bottom shows the on-trunk test setup. Reproduced with permission from ref [78]. Copyright 2016 The Author(s), under exclusive license to Springer Nature Express. (D) Thread-based glucose, pH, strain, and temperature sensors, microfluidic channels, and interconnects for the realization of a diagnostic device and bottom shows the measurement of strain indicate under diverse wound atmospheric condition. Reproduced with permission from ref [77]. Copyright 2016 The Author(due south), nether the Creative Commons Attribution License. (East) Physical sensors (pressure and moisture shown below) fastened to the flexible epitome wireless sensing arrangement mounted on mannequin leg. Reproduced with permission from ref [86]. Copyright 2014 The Authors. Published by Elsevier B.5.

Another instance relates to the bandage for monitoring irregular bleeding, pH levels, and external pressure at the wound site [78]. This bandage has depression-toll sensor integrated with a wireless monitoring system for continuous monitoring of wound healing, equally shown in Fig. half-dozen.6C. The output of the sensor shows 'Bandage OK' when there is no bleeding. When in that location is bleeding, the bandage communicates with the receiver which displays the 'Change Cast' sign [78]. Recently another new work reported thread-based sensors for the in vitro and in vivo analysis of glucose, pH, strain, and temperature levels [77]. The possibilities of simultaneous monitoring of pH and glucose in wound fluid past using fluorescence changes for different chemical methods have been explored also [84]. In that location is not much work in the area of bandage-based glucose sensors for wound monitoring. In addition to this, the measurement of tissue oxygenation is some other major wound healing inhibitors in chronic wounds [87]. A detailed written report is required for the development and embedding of such sensors in bandages for wound monitoring.

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How Cells Grow

Shijie Liu , in Bioprocess Engineering (2nd Edition), 2017

11.10 Outcome of pH

A hydrogen-ion concentration (pH) affects the activity of enzymes and therefore the microbial growth rate. The optimal pH for growth may be different from that for production formation. Mostly, the acceptable pH range varies about the optimum by 1 to two   pH units. Different organisms accept dissimilar pH optima: the pH optimum for many bacteria ranges from pH 3–8; for yeast, pH 3–half-dozen; for molds, pH iii–7; for plant cells, pH 5–6; and for animal cells, pH 6.five–7.v. Many organisms accept mechanisms to maintain intracellular pH at a relatively abiding level in the presence of fluctuations in environmental pH. When pH differs from the optimal value, the maintenance-energy requirements increase. 1 event of unlike pH optima is that the pH of the medium tin can be used to select i organism over another.

In most fermentations, pH can vary substantially. Often, the nature of the nitrogen source can be important. If ammonium is the sole nitrogen source, hydrogen ions are released into the medium as a issue of the microbial utilization of ammonia, resulting in a decrease in pH. If nitrate is the sole nitrogen source, hydrogen ions are removed from the medium to reduce nitrate to ammonia, resulting in an increase in pH. As well, pH can change because of the production of organic acids, the utilization of acids (particularly amino acids), or the production of bases. The evolution or supply of CO₂ can change pH greatly in some systems (eg, seawater or brute cell culture). Thus, pH control by means of a buffer or an active pH control organization is important. Variation of specific growth rate with pH is depicted in Fig. 11.eight, indicating a pH optimum.

Fig. eleven.8. A fictitious variation of a specific growth rate with pH. With some microbial cultures, information technology is possible to conform cultures to a wider range of pH values, if pH changes are made in small increments in each culture transfer.

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Ionic equilibrium reactions

J O Bird BSc, CEng, MIEE, CMath, FIMA, FCollP, MIEIE , P J Chivers BSc, PhD , in Newnes Engineering and Concrete Science Pocket Book, 1993

The pH scale

ten

The hydrogen ion concentration of one molar hydrochloric acrid, pure water and ane molar sodium hydroxide are i, 10 ⁻⁷ and 10⁻¹⁴ mol dm⁻³ respectively. It is convenient to construct a scale of simpler numbers to represent these values. This can be achieved by taking the reciprocal of the logarithm to the base of operations 10 of the hydrogen ion concentration of the solution. When the conversion is fabricated the value is called the pH value of the solution as shown past the conversions overpage.

When [H₃O⁺] = 1 mol dm⁻³,

$pH\text{value}=\frac{\mathrm{ane}}{{\log }_{10}\left[{\text{H}}_{\mathrm{iii}}{\text{O}}^{+}\right]}=-{\log }_{10}\left[{\text{H}}_3{\text{O}}^{+}\right]=-{\log }_{10}\mathrm{i}=0$

When [H₃O⁺] = 10⁻⁷ mol dm⁻³,

$pH\text{value}=\frac{1}{{\log }_{10}\left[{\text{H}}_3{\text{O}}^{+}\right]}=-{\log }_{10}\left[{\text{H}}_3{\text{O}}^{+}\right]=-{\log }_{10}{10}^{-\mathrm{seven}}=7$

When [H_threeO⁺] = ten⁻¹⁴ mol dm⁻³,

$pH\text{value}=\frac{\mathrm{ane}}{{\log }_{\mathrm{ten}}\left[{\text{H}}_{\mathrm{three}}{\text{O}}^{+}\right]}=-{\log }_{10}\left[{\text{H}}_{\mathrm{iii}}{\text{O}}^{+}\right]=-{\log }_{10}{10}^{-14}=\mathrm{fourteen}$

the pH scale has been selected with values between 0 and 14 corresponding to hydrogen ion concentration of ane mol dm⁻ⁱⁱⁱ and 10⁻¹⁴ mol dm⁻ⁱⁱⁱ. A cognition of the pH value of a solution gives a value for the hydrogen ion concentration of that solution. For example, if a solution of hydrochloric acid, HCl(aq), has a pH of 4. this means that for the solution, using the equation

$pH{\text{value=−log}}_{\text{10}}\left[{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}\right]\text{and so}{\text{4=−log}}_{\text{ten}}\left[{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}\right]$

Rearranging this expression gives

and taking antilogs gives

Hence the concentration of the acid must exist x ⁻⁴ K.

The adding of the hydrogen ion concentrations in weak acids from pH values does not give the concentration of the weak acid direct but if the degree of ionisation is known then the concentration can be found. For example, the pH of a solution of chloroethanoic acid is ane.72 when α = 0.064. This means that the hydrogen ion concentration of the solution given past the equation

and in the class [H₃ ⁺O] = antilog (-pH) is [H_iii ⁺O] = antilog (-i.72) or [H₃ ⁺O] = 0.019 mol dm⁻³. Past using the relationship

$\begin{array}{l}{\left[{\text{H}}_{\text{iii}}^{\text{+}}\text{O}\right]}_{\text{equil}}\text{=}{\left[{\text{H}}_{\text{3}}^{\text{+}}\text{O}\right]}_{\text{solution}}\text{×α}\\ \text{and then}\text{0}\text{.019=}{\left[{\text{H}}_{\text{3}}^{\text{+}}\text{O}\right]}_{\text{solution}}\text{×0}\text{.064}\\ \text{or}{\left[{\text{H}}_{\text{3}}^{\text{+}}\text{O}\right]}_{\text{solution}}\text{=}\frac{\text{0}\text{.019}}{\text{0}\text{.064}}\text{=0}\text{.three}\end{array}$

Hence the concentration of the acid must be 0.3 mol dm ^–3.

11

An equivalent calibration can be applied to the concentration of hydroxide ions using the definition

$pOH\text{=}\frac{\text{i}}{{\text{log}}_{\text{10}}\left[{\text{OH}}^{-}\right]}{\text{=-log}}_{\text{10}}\left[{\text{OH}}^{-}\right]$

12

On these combined scales of pH and pOH it tin be shown that because for water when pH = pOH = 7 that pH + pOH = 14. This relationship is useful in the interconversion of values. For example, the pOH at a 0.01 M solution of sodium hydroxide is 2, the pH of the aforementioned solution must be xiv-two = 12.

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Macromolecular Architectures and Soft Nano-Objects

J. Yuan , ... S.S. Sheiko , in Polymer Science: A Comprehensive Reference, 2012

6.06.four.2.2 pH-responsive molecular brushes

Potentiometric hydrogen ion concentration (pH) is an important stimulus, which can be addressed through pH-responsive materials. ^{311,330–335} Upon pH variation, ionizable polymers with a p1000 _a between 3 and 10 (weak acids and bases) exhibit a change in the ionization state leading to conformational changes. The classical monomers are acrylic acrid (AA), methacrylic acid (MAA), maleic anhydride (MA), and Due north,N-dimethylaminoethyl methacrylate (DMAEMA). For example, the pK _a of PAA depends on molecular weight and ranges within 6.eight–7 for molecular weights on the lodge of 100   kDa. ³³⁶ When the pH of the solution is below the pM _a value, the polymer is in a compact collapsed course. Equally the pH increases above the pChiliad _a, the polymer exhibits fully stretched conformation due to the electrostatic repulsion between the segments. ³³⁷ The unique properties of pH-responsive polymers ascend from the facile pH adjustment, which induces ionic interaction and hydrogen bonding, resulting in a reversible microphase separation or cocky-organisation phenomenon. Thus, pH-responsive polymeric systems provide the possibility of preparation of smart functional materials that can be used for potential therapeutic applications, for example, controlled drug delivery based on pH-triggered release.

Several strategies have been employed to demonstrate the consequence of pH on the conformation and aggregation behavior of molecular brushes. I strategy was to mimic proteoglycans – polyelectrolyte brush-like macromolecules present in the body ( Figure 65 ). They consist of a core poly peptide with loosely grafted glycosaminoglycan chains, which are long, linear carbohydrate polymers that are negatively charged nether physiological conditions. ^{162–165,339} The first instance of constructed substitutes for proteoglycans has been provided by Lienkamp et al. ^338,340 using cylindrical polyelectrolyte brushes from poly(styrenesulfonate) (PSS). Cylindrical polyelectrolyte brushes from PSS were synthesized by polymer analogous hydrolysis from the corresponding dodecyl and ethyl ester brushes. Information technology has been constitute that the aggregation behavior, size, and shape of the aggregates in solution depend on the side-concatenation length and the caste of saponification. The end-functionalized PSS polyelectrolyte brushes with a positively charged linker were synthesized and their complexation beliefs toward negatively charged latex particles was investigated.

Effigy 65. Cartoon representation of the proteoglycan–hyaluronic acrid aggregates in human cartilage (left) and a simplified synthetic model system for this structure (right).

Reprinted from Lienkamp, K.; Noe, L.; Breniaux, M.-H.; et al. Macromolecules 2007, 40 (vii), 2486–2502, with permission from ACS. ³³⁸

To investigate the effect of grafting density, Lee et al. ³⁴¹ prepared a serial of water-soluble loosely grafted PAA brushes with four different grafting densities by the 'grafting from' arroyo using ATRP. AFM was used to written report the conformation of adsorbed brushes equally a office of pH. As shown in Effigy 66 , the adsorbed molecules undergo a globule-to-extended conformational transition as the solution is inverse from acidic to bones. This transition was monitored on a mica surface by imaging individual molecules with AFM. The conformational behavior was compared with 100% grafted PAA brushes. Different the loosely grafted brushes, the 100% grafted molecules remained fully extended in a wide range of pH values (pH 2–9) due to steric repulsion between the densely grafted side chains, which is strongly enhanced upon adsorption to a substrate.

Figure 66. Loosely grafted PAA brushes: transformation from a compact globule to an extended molecule with an increase in pH.

Reprinted from Lee, H.-I.; Boyce, J. R.; Nese, A.; et al. Polymer 2008, 49 (25), 5490–5496, with permission from Elsevier. ³⁴¹

PDMAEMA is a unique stimuli-responsive polymer since it responds to temperature and also to pH in aqueous solution. It can also be permanently quaternized and converted to zwitterionic structures (via reaction with propanesultone), forming materials with UCST properties, equally described in the previous section. Xu et al. ¹¹⁵ prepared molecular brushes with PDMAEMA side bondage and the corresponding quaternized analog from a PBIEM backbone, and studied pH response of these polymers. As expected, the structural changes were induced by variation of pH, ranging from 2 to 10. At pH 7, the PDMAEMA brushes formed worm-similar structures that can exist quite curved. At pH 2, most of the brushes are protonated and ionized, showing more stretched morphologies. More than remarkably, at pH 10, the brushes are strongly contracted, with an average length around 110   nm, which is attributed to a collapse of the nonionized PDMAEMA side chains. pH-responsive PDMAEMA brushes were also synthesized from a conductive PT courage by Wang et al. ¹²⁷ They observed conformational transitions of PT-g-PDMAEMA with a change in pH, which contributed to spectral shifts. In dilute aqueous solution, the assimilation and fluorescence spectra of the polymer castor show sensitive and reversible pH responses. As shown schematically in Figure 67 , the polymer castor forms a more extended conformation with a decrease in pH from viii to 2. Protonation of the Me_twoN groups and increased repulsive interactions among the PDMAEMA side chains drive the redshift of the absorption and fluorescence spectra of the PT backbone.

Figure 67. Proposed machinery for the molecular conformational transition accompanying the change of solvent polarity or the change of pH in h2o.

Reprinted from Wang, Thou.; Zou, South.; Guerin, G.; et al. Macromolecules 2008, 41 (19), 6993–7002, with permission from ACS. ¹²⁷

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Evaluating Drilling Fluid Performance

Ryen Caenn , ... George R. , in Composition and Properties of Drilling and Completion Fluids (Seventh Edition), 2017

Hydrogen Ion Concentration (pH)

The meaning influence of the hydrogen ion concentration on the backdrop of water-based drilling fluids has long been recognized and has been the bailiwick of numerous studies. Hydrogen ion concentration is more conveniently expressed every bit pH, which is the logarithm of the reciprocal of the hydrogen ion concentration in gram moles per liter. Thus, in a neutral solution the hydrogen ion (H ⁺) and the hydroxyl ion (OH⁻) concentrations are equal, and each is equal to 10⁻⁷. A pH of 7 is neutral. A subtract in pH below 7 shows an increase in acerbity (hydrogen ions), while an increment in pH in a higher place 7 shows an increase in alkalinity (hydroxyl ions). Each pH unit of measurement represents a ten-fold change in concentration.

Two methods for the measurement of pH are in common use: (1) a colorimetric method using paper test strips impregnated with indicators; and (2) an electrometric method using a glass electrode instrument.

Colorimetric method. Newspaper examination strips impregnated with organic dyes, which develop colors characteristic of the pH of the liquid with which they come in contact, afford a simple and user-friendly method of pH measurement. The rolls of indicator paper are taken from a dispenser that has the reference comparison colors mounted on its sides. Test papers are available in both a broad-range type, which permits estimation of pH to 0.five units, and a narrow-range type, which permits interpretation to 0.2 units of pH. The examination is fabricated past placing a strip of the paper on the surface of the mud (or filtrate), allowing information technology to remain until the color has stabilized (usually <30   south), and comparison the colour of the paper with the color standards. High concentrations of common salt in the sample may alter the color adult by the dyes and cause the gauge of pH to be unreliable.

Glass electrode pH meter. When a sparse membrane of glass separates two solutions of differing hydrogen ion concentrations, an electrical potential difference develops that tin be amplified and measured. The pH meter consists of (ane) a glass electrode made of a thin-walled seedling of special drinking glass within which is sealed a suitable electrolyte and electrode; (2) the reference electrode, a saturated calomel jail cell; (three) a means of amplifying the potential deviation between the external liquid (mud) and the glass electrode; and (4) a meter reading directly in pH units. Provision is fabricated for calibrating with standard buffer solutions and for compensating for variations in temperature. A special glass electrode (less affected by sodium ions) should be used in measuring the pH of solutions containing high concentrations of sodium ions (high salinity or very high pH).

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Respiratory Alkalosis and Acidosis

Nicolaos E. Madias , Horacio J. Adrogué , in Seldin and Giebisch'southward The Kidney (Fourth Edition), 2008

Intracellular pH During Respiratory Alkalosis

"Whole-torso" intracellular hydrogen-ion concentration, as assessed past the DMO (5,5-dimethyl-ii,four-oxazolidinedione) method, has been found to fall in parallel with extracellular hydrogen-ion concentration when salubrious human subjects hyperventilate voluntarily to reach a PaCO₂ of fifteen–20 mm Hg. Similar results take been obtained from studies in dog and rat muscle and rat brain. On the other hand, ³¹P-nuclear magnetic resonance (NMR) spectroscopy has revealed much smaller changes in canine center intracellular pH in response to astute hypocapnia equally compared with the extracellular compartment (49). The response of intracellular acerbity to chronic hypocapnia has not been studied.

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Chemistry, Microbiology and Biology of Water

Malcolm J. Brandt BSc, FICE, FCIWEM, MIWater , ... Don D. Ratnayaka BSc, DIC, MSc, FIChemE, FCIWEM , in Twort's H2o Supply (Seventh Edition), 2017

7.38 pH Value or Hydrogen Ion

The pH value, or hydrogen ion concentration, determines the acerbity of a h2o. It is ane of the most important determinations in water chemical science every bit many of the processes involved in water treatment are pH dependent. Pure water is very slightly ionized into positive hydrogen (H ⁺) ions and negative hydroxyl (OH⁻) ions. In very full general terms a solution is said to be neutral when the numbers of hydrogen ions and hydroxyl ions are equal, each corresponding to an approximate concentration of ten⁻⁷  moles/l. This neutral indicate is temperature dependent and occurs at pH 7.0 at 25°C. When the concentration of hydrogen ions exceeds that of the hydroxyl ions (i.eastward. at pH values less than seven.0) the water has acidic characteristics. Conversely, when there is an excess of hydroxyl ions (i.e. the pH value is greater than 7.0) the water has bones characteristics and is described as existence on the alkaline side of neutrality.

The pH value of unpolluted water is mainly determined by the inter-human relationship between free carbon dioxide and the amounts of carbonate and bicarbonate nowadays (Section ten.41). The pH values of most natural waters are in the range 4–9, with soft acidic waters from moorland areas generally having lower pH values and hard waters which have percolated through chalk or limestone more often than not having college pH values.

Most water treatment processes, but peculiarly clarification and disinfection, require careful pH control to optimize the efficacy of the process fully. The pH of the h2o entering distribution must too be controlled to minimize the corrosion potential of the water (Department 7.21).

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Measurement of (H+) and CO2

P.D. Davis BSc CPhys MIstP MIPSM , ... Yard.N.C. Kenny BSc (Hons) Doctor FRCA , in Basic Physics and Measurement in Amazement (Fourth Edition), 1995

Publisher Summary

This affiliate discusses the measurement of hydrogen ion concentration and carbon dioxide in clinical aspects. pH is a measure of the hydrogen ion activity in a liquid. Hydrogen ion activeness is not exactly the same as hydrogen ion concentration (H ⁺), just for practical purposes in the clinical situation, these may be regarded as equivalent. This chapter illustrates a (H⁺) electrode associates. The (H⁺) electrode is an case of an ion-selective electrode, and information technology depends for its operation on an hydrogen-ion sensitive glass at its tip. A potential develops across this glass, which depends on the difference of (H⁺) across information technology. The (H⁺) within the (H⁺) electrode is maintained at a constant value by a buffer solution and then that the potential across the glass is dependent on the (H⁺) in the blood sample in the aqueduct.

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The Soil Arrangement

Abdel-Mohsen Onsy Mohamed , Evan Yard. Paleologos , in Fundamentals of Geoenvironmental Engineering, 2018

four.10.six The pH and p(x) Concept

In 1909 Sorensen proposed to express the hydrogen-ion concentration in an aqueous solution in terms of its negative logarithm and designated such values every bit pH⁺. His symbol has been superseded by the simple designation pH. The terms may be represented by

(iv.27) $\mathrm{p}\mathrm{H}=-log\left\{{\mathrm{H}}^{+}\right\}\mathrm{or}\mathrm{p}\mathrm{H}=log\frac{\mathrm{i}}{\left\{{\mathrm{H}}^{+}\right\}}$

With water and in the absence of foreign materials, activity equals tooth concentration and [H⁺] equals [OH⁻] every bit required by electroneutrality, and the product at 25°C equals Thousand _w or 10–14. These atmospheric condition mean that {H⁺}   =   {OH⁻}   =   10^{−   vii} , and the pH equals seven, which is considered the "neutral" pH for water. The pH scale is normally represented as ranging from 0 to xiv. Values of pH lower than seven betoken that the hydrogen ion concentration is greater than the hydroxide ion concentration, and the aqueous solution is termed acidic. The opposite status is implied when the pH exceeds seven, and the aqueous solution is termed basic.

pH is the chemical holding that affects various chemic processes in soils. In general, potentially toxic metals cations are most mobile under acrid weather condition and increasing the pH by liming usually reduces their bioavailability. However molybdate anions become more bachelor with increasing pH (Alloway, 1995).

The method of expressing hydrogen ion activity or concentration as pH is also useful for expressing other pocket-sized numbers such equally the concentration of other ions or ionization constants for solutions of weak acids and bases. For this purpose, the p(x) notation is used, with p(x) defined as

(iv.28) $p\left(x\right)=-{log}_{10}\left(x\right)={\log }_{10}\frac{1}{\mathrm{10}}$

Here the quantity x may exist the concentration of a given chemical species, an equilibrium constant, or the similar. Thus, merely as pH is the negative logarithm of the hydrogen ion activity, pOH signifies the negative logarithm of the hydroxide ion activity, and the pK _w the negative logarithm of the ionization abiding for water. From the mass reaction equation for h2o,

(4.29) $\left\{{\mathrm{H}}^{+}\right\}\left\{{\mathrm{O}\mathrm{H}}^{-}\right\}={\mathrm{Grand}}_{\mathrm{w}}$

It follows that

(4.30) $-log\left\{{\mathrm{H}}^{+}\right\}-log\left\{{\mathrm{O}\mathrm{H}}^{-}\right\}=-log{K}_{\mathrm{westward}}$

and that

(4.31) $\mathrm{p}\mathrm{H}+\mathrm{p}\mathrm{O}\mathrm{H}=\mathrm{p}{\mathrm{Chiliad}}_{\mathrm{w}}$

Since K _w  =   one   ×   10^{−   14} at 25°C, information technology follows that at this temperature pYard _{due west}  =   14.

For weak acids and bases, pK_A is the negative logarithm of the ionization constant for weak acids, and pK_B is the negative logarithm of the ionization constant for weak bases. The ionization constants and pK_A and pThousand_B values for several weak acids and bases of interest to geoenvironmental applied science are listed in Tables 4.eleven and iv.12 (Sawyer et al., 1967).

Table iv.11. Typical Ionization Constants for Weak Acids at 25°C

Acrid	Equilibrium equation	GA	pThousandA
Acetic	CH3COOH   ↔   H   +   CH3COO−	i.8   ×   10−   5	4.74
Ammonium	NH4 +  ↔   H+  +   NHthree	five.56   ×   10−   10	9.26
Boric	HiiiBO3  ↔   HiiBOiii −	5.8   ×   10−   ten	ix.24
Carbonic	H2CO3  ↔   H+  +   HCOthree −	four.3   ×   x−   7	six.37
	HCOthree −  ↔   H+  +   CO3 −	four.vii   ×   x−   11	ten.33
Hydrocyanic	HCN   ↔   H+  +   CN−	4.8   ×   10−   x	9.32
Hydrogen Sulfide	H2S   ↔   H+  +   HS−	9.1   ×   ten−   8	vii.04
	HS-   ↔   H+  +   Due south2   −	1.three   ×   10−   13	12.89
Hypochlorous	HOCl   ↔   H+  +   OCl−	2.9   ×   ten−   eight	7.54
Phenol	C6H5OH   ↔   H+  +   C6H5O−	1.2   ×   10−   10	9.92
Phosphoric	H3PO4  ↔   H+  +   HiiPO4 −	7.5   ×   10−   3	two.12
	H2POiv −  ↔   H+  +   HPO4 2   −	half dozen.two   ×   10−   8	7.21
	HPO42−  ↔   H+  +   PO4 3   −	4.8   ×   x−   thirteen	12.32
Propionic	CH3CHtwoCOOH   ↔   H+  +   CH3CH2COO−	1.3   ×   ten−   5	4.89

Adapted from Sawyer, C.N., McCarty, P.L., Parkin, G.F., 1967. Chemistry for Environmental Engineering. McGraw Hill, Inc., New York, 658p.

Table 4.12. Typical Ionization Constants for Weak Bases and Salts of Weak Acids at 25°C

Substance	Equilibrium equation	MA	pKA
Acetate	CH3COO−  +   HiiO   ↔   CHiiiCOOH   +   OH−	5.56   ×   10−   x	9.26
Ammonia	NH3  +   H2O   ↔   NHfour +  +   OH−	ane.viii   ×   10−   5	four.74
Borate	H2BO3 −  +   HiiO   ↔   H3BO3  +   OH−	i.72   ×   10−   v	iv.76
Carbonate	CO3 2   −  +   H2O   ↔   HCOiii −  +   OH−	2.13   ×   10−   4	three.67
	HCO3 −  +   H2O   ↔   HtwoCO3  +   OH−	ii.33   ×   10−   8	7.63
Calcium hydroxide	CaOH+  ↔   Catwo   +  +   OH−	3.5   ×   x−   2	1.46
Magnesium hydroxide	MgOH+  ↔   Mgii   +  +   OH−	ii.half dozen   ×   ten−   3	2.59

Adjusted from Sawyer, C.N., McCarty, P.L., Parkin, G.F., 1967. Chemistry for Environmental Applied science. McGraw Hill, Inc., New York, 658p.

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