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Fossil fuel combustion results in rising atmospheric carbon dioxide (CO2), which is known to impact the global climate and the oceans. Latest insights indicate that rising atmospheric CO2 levels also affect CO2 partial pressure (pCO2) in freshwaters, where pCO2 is controlled by a multitude of parameters. However, up to date there is no standardized method, which allows the determination of current and past freshwater pCO2 levels. Ideally methods should incorporate numerous hydrogeochemical and -physical factors to reflect the interplay of all interacting components and their effect on pCO2. We here describe the application of the geochemical program PHREEQC. This freeware serves as an easy method enabling a plausible and comprehensive analysis of pCO2 for field, laboratory, and especially long-term data. We present the use of the different input parameters of a laboratory- and a field long-term monitoring dataset including dissociation constants of carbonic acid measured as total inorganic carbon (TIC) and total CO2 concentration (TCO2) or total alkalinity (TA), together with hydrogeochemical and -physical parameters. Based on current literature and our analyses PHREEQC appears a solid strategy to determine freshwater pCO2 that can moreover be used for long-term datasets.•Comprehensive analysis of pCO2 for field, laboratory, and long-term data.•PHREEQC is not dependent on just one sampling method or parameter scheme.•PHREEQC includes testing the plausibility of a water analysis and enables the assessment of the quality of the laboratory analysis, as well as automatic calculation of all relevant aquatic complexes., Graphical Abstract Image, graphical abstract

One-third of the CO2 released in the atmosphere by anthropogenic activities is absorbed by the oceans determining a dramatic change in seawater chemistry. In fact, CO2 reacts with water to form carbonic acid (H2CO3), which being unstable dissociates into hydrogen ions (H+) and bicarbonate ( H C O 3 − ) . Diatoms are a crucial component of the biological carbon pump that exports carbon into the ocean, contributing significantly to the long-term sequestration of atmospheric CO2. Diatom genome sequencing reveals the presence of different systems for H C O 3 − uptake, most of which are phylogenetically affiliated with those found in metazoans. In Phaeodactylum tricornutum, a plastid-targeted β-CA suggests that the localization and the role of carbonic anhydrases in diatoms are central to primary carbon metabolism. This chapter focuses on the δ-CAs (TweCA) identified in the genome of the marine diatom Thalassiosira weissflogii, demonstrating that TweCA is catalytically active for the hydration of CO2 but not for the hydrolysis of p-nitrophenyl acetate. Besides, the phylogenetic analysis showed that the δ-CAs are phylogenetically correlated more with the α-CAs than the other CA classes. Moreover, inhibition profiles of sulfonamides, inorganic anions, and the mono- and dithiocarbamates showed distinctive features for this enzyme providing new insights into the role of δ-CA in the algal carbon-concentrating mechanism.

Most caves owe their origin to carbonic acid generated in the soil. In contrast, sulfuric acid caves are produced by the oxidation of sulfides beneath the surface. Although sulfuric acid caves are relatively few, they include some large and well-known examples, such as Carlsbad Cavern, New Mexico. They also provide evidence for a variety of deep-seated processes that are important to petroleum geology, ore geology, tectonic history, and the nascent field of karst geomicrobiology.

Proton caged compounds exhibit a characteristic behavior when directly dosed into cells or being coupled to gold nanoparticles prior to the dosing. When irradiated in the near ultraviolet region, they release protons that interact with intracellular HCO3− to yield H2CO3. The dissociation of carbonic acid, then, releases CO2 that can be distinctively singled out in infrared spectra.In the process of searching a pathway to augment the intracellular uptake of proton caged compounds, we probed the association of 1-(2-nitrophenyl)-ethylhexadecyl sulfonate (HDNS) with DMSO, an agent to enhance the membrane permeability. We found out a different UV-induced protonation mechanism that opens up to new conduits of employing of proton caged compounds. Here, we report the infrared data we collected in this set of experiments. Keywords: Proton caged compounds, DMSO, Intracellular proton release

To develop reaction systems of chemical conversion of biomass, fructose was heated in an aqueous medium under pressurized CO2, which caused in situ generation of carbonic acid. It gave 5-hydroxymethyl-2-furfural (HMF) as a dehydration product in good yields. The maximum yield of HMF was 92% in the reaction at 90 °C under 7.0 MPa of CO2 for 168 h. The reaction proceeded in the absence of any other reagents such as non-volatile acids, organic solvents, inorganic, and organic salts. It means green, environmental-friendly, and efficient process was achieved for production of HMF., Tetrahedron Letters, 57(42), pp.4742-4745; 2016

Water represents ∼65% of the weight of an adult human. Water is distributed in the intracellular (ICF) and an the extracellular (ECF) compartments. This last includes the intravascular space, and the interstitial fluid. Daily water ingestion is ∼2500 mL. A similar amount is eliminated per day through the urine, feces, skin, and lungs. The main ECF cation is Na+, while the major cation in the ICF is K+. Among the anions, Cl− predominates in the ECF; phosphates, sulfates, and proteins are found in the ICF. The presence of proteins (which behave as anions at the pH of biological fluids) in compartment spaces surrounded by semipermeable membranes determines an uneven distribution of diffusible ions. This phenomenon, called the Gibbs–Donnan equilibrium, plays an important role in cell volume and osmotic stability. The osmolarity of plasma is ∼300 mOsm/L. Regulation of ECF osmolarity and volume depends mainly on renal activity and the mechanism of thirst. Oncotic pressure is the osmotic pressure exerted by the proteins present in body fluids. The difference in oncotic pressure between blood and the interstitial space, and its balance with the capillary hydrostatic pressure (Starling equilibrium) helps maintain fluid exchange in the interstitial space. Dehydration and hyper hydration are alterations in the body water balance. They can present without changes in osmolarity (isotonic with respect to normal plasma), or can be accompanied by increased or reduced osmolarity (hypotonic or hypertonic, respectively). Acid–base balance is essential to cope with the continuous changes in pH due to intake and production of acids and bases in the body. Several buffer systems operate in the body. In the intracellular space proteins (Prot−/ProtH) and phosphates (HPO42−/H2PO4−) function as buffer systems. In the intravascular space, the main buffer is hemoglobin. In the ECF the bicarbonate/carbonic acid pair is the most important buffer system. CO2 produced by cellular activity, dissolves in body fluids and is hydrated in a reaction catalyzed by carbonic anhydrase to give carbonic acid, which rapidly ionizes into bicarbonate and H+. The H2CO3− concentration depends on the amount of CO2 dissolved and PCO2PCO2. At normal pH (7.4), the ratio [HCO3−]/[CO2] value is 20. Bicarbonate/carbonic acid regulation is achieved by close control of the HCO3−/CO2 system. This takes place at two main levels: (1) The respiratory system , which responds to blood pH and PCO2PCO2 changes acting on the respiratory center. A decrease in pH or increase in PCO2PCO2 stimulates the frequency and depth of breathing, augmenting CO2 removal. PCO2PCO2 reduction or pH increase depress pulmonary ventilation and promotes CO2 accumulation in blood. (2) Renal regulation controls body pH via three main mechanisms: bicarbonate reabsorption, urine acidification, and production of ammonium ions. Changes in pH in the renal tubular cells modify the activity and expression of the mechanisms involved in H+ and HCO3− transport. Increased H+ secretion enhances HCO3− reabsorption and acid excretion. Disorders of acid–base balance are characterized by modifications of the HCO3−/CO2 system. Depending on the alteration, four types of acid–base alterations can be distinguished: (1) Respiratory acidosis consists of a decrease in pH originated by alterations in pulmonary ventilation, which reduce CO2 removal and increase the partial pressure of PCO2PCO2; (2) Metabolic acidosis is the drop in pH caused by a primary reduction in plasma bicarbonate and it is produced by excessive loss of bicarbonate, retention or intake of acids. It can be caused by renal insufficiency; (3) Respiratory alkalosis is the condition characterized by the increase in pH in which the primary alteration is the decrease in PCO2PCO2, due to situations that produce pulmonary hyperventilation; (4) Metabolic alkalosis, is the state caused by a primary increase in bicarbonate, which elevates blood pH, due to excessive intake of alkali or the excessive removal of acids from the body. Respiratory and metabolic acidosis and alkalosis may be uncompensated or compensated if the systems of regulation function efficiently.

WOS: 000387626500095, 27773315, The effects of the homogenization process on the structures and dielectric properties of pure and Nb-doped BaTiO3 ceramics have been investigated using an ultrasonic homogenization and conventional mechanical methods. The reagents were homogenized using an ultrasonic processor with high-intensity ultrasonic waves and using a compact mixer-shaker. The components and crystal types of the powders were determined by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The complex permittivity (epsilon', epsilon'') and AC conductivity (sigma') of the samples were analyzed in a wide frequency range of 20 Hz to 2 MHz at room temperature. The structures and dielectric properties of pure and Nb-doped BaTiO3 ceramics strongly depend on the homogenization process in a solid-state reaction method. Using an ultrasonic processor with high-intensity ultrasonic waves based on acoustic cavitation phenomena can make a significant improvement in producing high-purity BaTiO3 ceramics without carbonate impurities with a small dielectric loss. (C) 2016 Elsevier B.V. All rights reserved., scientific research projects coordination units at Mustafa Kemal University [326], This research was supported by the scientific research projects coordination units at Mustafa Kemal University (Grant no = 326). The authors are grateful to MARGEM, Mustafa Kemal University, for helping to collect SEM data and LCR data. The authors gratefully acknowledge support from HUMEL, Harran University, for helping to collect XRD data.

Corrosion in solutions of acidic gases, notably carbon dioxide and hydrogen sulfide, is very important in oil and gas production and can be expected to become important in processes for the sequestration of carbon dioxide. Carbon dioxide exhibits an equilibrium between dissolved CO 2 and carbonic acid, and this effectively buffers the hydrogen ion concentration, such that the rate of hydrogen evolution is much higher than for a solution of a strong acid with the same pH. Corrosion in CO 2 solution can be modeled using conventional electrochemical kinetic theory, and the results are in good agreement with experimental observations. Corrosion in H 2 S solution is less well understood, but models can be developed based on the premise that corrosion occurs through surface films of iron sulfide.

Salisbury biochar (produced from British broadleaf hardwood) with two different particle sizes (≤2mm and ≤0.15mm) was applied on a kaolin with three different lead (Pb(2+)) contamination levels (50mg/kg, 300mg/kg and 1000mg/kg) at the dosage of 1% in w/w. The short-term impact of biochar on the mobility and speciation of Pb(2+) in the kaolin was investigated using attenuation periods of 1, 7 and 28 days. The leachability and extractability of Pb(2+) in carbonic acid leaching and EDTA extraction tests as well as the speciation of Pb(2+) in soils were not significantly affected by biochar treatment during all periods. The insignificant effects of biochar on Pb(2+) immobilisation were most likely attributed to the high adsorption capacity of Pb(2+) on the kaolin and biochar failed to competitively adsorb Pb(2+) against kaolin. The kaolin immobilised Pb(2+) primarily through cation exchange, which represents the readily bioavailable fractions of Pb(2+) in soils and may still pose environmental risks. This paper suggests the inefficiency of biochar treament on heavy-metal contaminated clay-rich soils. Therefore a laboratory treatablity study with respect to the soil type may be crucial when large-scale biochar applications in heavy-metal associated soil remediation are evaluated.

This chapter discusses the application of sub- and supercritical water for hydrolysis of biopolymer into useful biochemicals, taking cellulose and protein as representative compounds, for biomass waste recycling. It includes the reviews of water properties as a solvent and catalyst for hydrolysis, reactor design and techniques for high-temperature and high-pressure experiments. Several literature focusing on recovery of bioactive compounds from the degradation of the two above-mentioned natural biopolymers from various starting materials are summarized. In addition, carbonic acid enhancement and coupling with microwave, electrolysis and plasma to enhance reaction or extraction rates is also discussed.

Carbon dioxide (CO 2 ) narcosis is related to ventilatory failure causing a respiratory acidosis due to an increase in the partial pressure of CO 2 in the arterial blood. When this happens acutely, the CO 2 combines with water to form carbonic acid. When this occurs intracellularly, there is an adverse effect on enzyme systems, ultimately leading to energy failure in brain cells. There is also a decrease in high-energy phosphates and an increase in the lactate:pyruvate ratio. In addition, there is an increase in cerebral blood flow, which can produce increased intracranial pressure. Treatment involves correcting precipitating causes and increasing ventilation, sometimes requiring a ventilator.

Anthropogenic sulfur dioxide (SO2) is principally the product of energy conversion through combustion of fossil fuel sources. This pollutant causes acidic rain and can also be harmful for human health. Many means for controlling sulfur dioxide emission are available in the market and have been extensively applied. Among these techniques, wet flue gas desulfurization is one of the most widely used methods because of its reliability and high efficiency. Nonetheless, high energy and water consumption are among its principal drawbacks. Limestone dissolution has been accounted as one of the main controlling steps of the process ( Pepe, 2001 ). Even though limestone is dissolved in acidic media in many industrial processes worldwide, no commonly accepted mathematical models exist for the dissolution kinetics at the moment. The reasons for the contradictory results in literature dwell, at least to considerable extent, from the varying influence of mass transfer limitations and the influence of CO2 on the pH. Experimental equipment and a methodology for evaluating the kinetic regime of a high grade limestone commercially used for desulfurization was developed in the current study. The results show that the kinetic regime, necessary to properly characterize the dissolution rate, can be reached even with small particle size and high temperatures with the help of severe agitation to overcome solid-liquid mass transfer and powerful purging to minimize the influence of carbonic acid on the pH. The method can be directly applied for investigating and comparing the reactivities of various limestone samples for industrial purposes.

Polycarbonates (PCs) are polyesters of diols or diphenols and carbonic acid containing –OC(O)O– groups in their backbone chains and therefore can be divided into aliphatic and aromatic ones. An alternative method for PC synthesis is ring-opening polymerization (ROP) of cyclic carbonates, both aliphatic and aromatic ones. Aliphatic PCs and copolycarbonates, due to their biocompatibility and biodegradability, are valuable biomaterials and stimulate intensive efforts to develop new synthetic methods. Incorporation of the carbonate structure provides flexibility and toughness to the otherwise rigid and brittle polyesters.

Corrosion in solutions of acidic gases, notably carbon dioxide and hydrogen sulfide, is very important in oil and gas production and can be expected to become important in processes for the sequestration of carbon dioxide. Carbon dioxide exhibits an equilibrium between dissolved CO2 and carbonic acid, and this effectively buffers the hydrogen ion concentration, such that the rate of hydrogen evolution is much higher than for a solution of a strong acid with the same pH. Corrosion in CO2 solution can be modeled using conventional electrochemical kinetic theory, and the results are in good agreement with experimental observations. Corrosion in H2S solution is less well understood, but models can be developed based on the premise that corrosion occurs through surface films of iron sulfide.

[1] The transport of gas phase carbon dioxide through unsaturated soils has the potential to significantly alter the soil biogeochemistry. Leakage of CO2 from deep reservoirs, either naturally occurring or anthropogenically emplaced, may displace oxygen in the soil gas and hence radically alter the redox conditions of a soil. Furthermore, the formation of carbonic acid in the aqueous phase will alter the pH of the soil system. A two-dimensional numerical model has been developed to explore the effects of gaseous CO2 leakage on the biogeochemistry of a variably saturated porous media. The model describes the sequential degradation of organic carbon by microorganisms using a series of terminal electron acceptors. Gas phase CO2 intrusion results in changes in redox conditions and pH of the soil water, both of which lead to alteration of the biogeochemistry of the soil. Alteration of the biogeochemical profile of a representative field site is explored with the numerical model.

Aldol reaction of propanal was carried out by using basic catalysts of MgO with different particle size under supercritical CO2 in the presence or absence of water. The obtained results showed that the catalytic activities of MgO depended on the order of catalyst size in the absence of water. In contrast, size dependence of the catalytic activity could not be observed in the reaction system, whereas the activity was improved by the addition of water. TEM and XRD analyses revealed that microscopic structure of MgO was converted to hydromagnesite after the reaction, since carbonic acid dissolved MgO during the reaction in the presence of water. The roles of MgO catalysts and carbonic acid in aldol reaction were discussed.

This chapter discusses the concept of equilibrium for solutions and metal complex ions. It addresses several issues, such as a fizzing action that occurs when an antacid tablet dissolves in water. The effervescence of an antacid tablet in water is the key to the effectiveness of the antacid. Two familiar antacids, such as Alka-Seltzer and Bromo Seltzer contain sodium bicarbonate or baking soda—NaHCO 3 . The bicarbonate ion reacts with citric acid, another ingredient of the product, to produce carbonic acid, H 2 CO 3 . In solution, carbonic acid decomposes to yield water and gaseous carbon dioxide, CO 2 , the same gas in carbonated beverages and champagne. The fizz generated when the tablet dissolves is simply the CO 2 bubbles coming out of solution. The chapter also discusses the functioning of the antidotes for cyanide poisoning, the chemical action of unclogging drains with household products, use of sequestrants in processed food items, and so on.

This chapter discusses the nucleophilic reactions on the carboxyl carbons present in carbonyl compounds and carboxyl compounds. The type of nucleophilic reaction that occurs depends exclusively on the nature of the substrate and hardly at all on the nucleophile. The typical reaction of carbonyl compounds with nucleophiles is the addition; the C=O bond disappears. Ketenes and other C=O-containing heterocumulenes also react with nucleophiles in addition reactions; the C=O double bond, however, is nonetheless retained. In contrast, C=O-containing carboxylic acid and carbonic acid derivatives react with nucleophiles in substitutionreactions. S N reactions convert carboxylic acid derivatives to other carboxylic acid derivatives, or convert carbonic acid derivatives to other carbonic acid derivatives, when a nucleophile containing a heteroatom attacks at the carboxyl carbon. When an organometallic compound is used as the nucleophile, S N reactions at the carboxyl carbon make it possible to synthesize aldehydes (from derivatives of formic acid), ketones, or—starting from carbonic acid derivatives— in some cases carboxylic acid derivatives. Similarly, when using a hydride transfer agent as the nucleophile, SN reactions at a carboxyl carbon allow the conversion of carboxylic acid derivatives into aldehydes. A key intermediate common to all of S N is the species in which the nucleophile is linked with the former carboxyl carbon for the first time. The tetrahedral intermediate is a high-energy intermediate. The larger the rate constant K add for the formation of the tetrahedral intermediate, the faster an acylating agent reacts with nucleophiles.

Knowledge of the impact of N-fertilizers on the weathering-erosion processes of soils in intensively cultivated regions is of prime importance. Nitrification of NH4− fertilizers produces HNO3 in the basin of the Garonne river, enhancing soil degradation. Their influence on the weathering rates was determined by calculating the consumption rate of atmospheric/soil CO2 by soil weathering and erosion, and its contribution to the total dissolved riverine HCO3−. This contribution was found to be less than 50% which corresponds normally to a complete carbonate dissolution by carbonic acid, suggesting that part of the alkalinity in the river waters is due to carbonate dissolution by an acid other than carbonic acid, probably HNO3.

This paper reports theoretical and experimental studies of physico-chemical properties of CO 2 hydrate and the stability of liquid CO 2 in water. Kinetics and mechanism of the formation of CO 2 hydrate at the interface between liquid CO 2 and water were investigated. Shrinkage rate of liquid CO 2 droplet in water at high pressures of 28 MPa and 35 MPa at 3° was measured. Bromocresol green was employed as a pH indicator to monitor the profile of carbonic acid distribution. The diameter of liquid CO 2 droplet reduced gradually with the rate of 5.0×10 -7 m/s. Furthermore, the stability of liquid CO 2 in seawater at 37 MPa was experimentally investigated by observing the pH and temperature changes around liquid CO 2 . There was no distinct change of the state of liquid CO 2 at 37 MPa. This paper proposes a new concept of deep sea CO 2 sequestration which allows long-term storage of liquid CO 2 at seabed. The ecological impacts of CO 2 will be greatly reduced because of the controlling effect of hydrate film on the dissolution of CO 2 into the seawater.

In field experiments, we tested an original technology to enhance oil recovery based on the activation of the stratal microflora of flooded oil fields. The technology includes the injection of aerated fresh water with added mineral salts. The activity of microflora (aerobic and anaerobic) increased sharply in the near-bottom zone of the injection well. The microbiological processes occurred in two stages. The first stage includes the activation of aerobic oxidation of organic matter in the oil, which leads to the formation of oil displacement agents, such as organic acids, surfactants, polysaccharides, and carbonic acid. During the second, anaerobic stage gases, methane, and carbonic acid were formed. The field tests were carried out in three pilot tests of different waterflooded areas of the Romashkino field. The additional oil that was recovered reached a total of 41.08 t.t, that was 32.9% of the total pilot production. The enhancement of oil recovery correlated with the rate of methanogenesis. The carbon isotope composition of the carbonates of stratal waters and the concentration of one of the main degradation products (acetate) were changed.

Publisher Summary This chapter discusses the degradation of organic matter by a suite of redox processes in marine sediments, with an emphasis on the effect on pore water chemistry, the modeling of concentration profiles, and the calculation of the concomitant fluxes across the sediment, water interface. Labile organic compounds are decomposed at more moderate rates and become buried in the sediment. The accumulation of organic matter in the sediments is a function of: (1) primary production in the photic zone above; (2) the total sedimentation rate; and (3) the porosity of the sediment. Decomposition of organic matter occurs mainly by micro-biota under oxic, suboxic, and anoxic conditions. As a result of the decomposition of carbonic acid, may be either produced or consumed, bicarbonate is formed. This affects the pH of the interstitial water. In addition to the role played by the degradation of organic matter, other reactions may also have an impact on changes in pore-water chemistry. Sediments consist of a mixture of solid particles immersed in pore waters. Studies of pore-water chemistry are used to estimate the consumption of oxygen, nitrate, and sulphate, as well as to estimate the methane production involved in the breakdown of organic matter. Finally, the chapter also presents several models that have been applied to measure profiles for oxygen, nitrate, manganese, sulfate, sulfide, methane, bicarbonate, phosphate, and silica in pore water.

Publisher Summary The chapter focuses on the reactions of carbon monoxide without transition-metal catalysis. The majority of these reactions involve organometallic reagents. The reactions of synthetic importance in the industry and laboratory, and carbonylations catalysed by transition metals are discussed. An interesting synthesis of isoindolinones from aryl halides uses sequential incorporation of molecular nitrogen and carbon monoxide at atmospheric pressure is presented. The reactions of carbon monoxide incorporated into metal carbonyls are reviewed. The subsections present ruthenium, chromium, cobalt, iron, and the use of metal carbonyl complexes to achieve enantioselective preparations are surveyed. The preparation and reactions for the compounds isocyanides and isonitriles are explained. The important topic on carbonic acid and derivatives is provided with the structure diagrams, equations and examples. The use of phosgene to prepare a variety of five- and six-membered heterocycles is reviewed. The preparations and reactions of orthocaronates are reviewed and presented.

Publisher Summary This chapter describes a large-scale treatment of acid mine drainage including a bacterial oxidation system, as an example of an effective and practical application of the bacteria. Thiobacillus ferrooxidans, found naturally in acid mine drainage, increases the oxidation of sulfide minerals and supplies ferrous ion in the acid drainage as the microbial catalyst. Utilizing these characteristics of Thiobacillus ferrooxidans, bacterial oxidation is being adopted in the treatment of acid mine drainage at some mines in Japan. To neutralize acid mine drainage and at the same time precipitate heavy metals, lime neutralization has been used for many years, employing calcium hydroxide in many cases. In comparison, neutralization by calcium carbonate has several advantages—such as lower cost, less volume, and faster settling of the resultant sludge. However, calcium carbonate simultaneously generates carbonic acid in the course of neutralization, which limits the maximum pH of the drainage to about 6.5. At this pH, the ferrous salt remains in solution and does not precipitate. If the ferrous salt can be oxidized to a ferric salt prior to neutralization, calcium carbonate is made available to neutralize acid mine drainage.

It has been suggested that in the absence of a catalytic mechanism, the rate of H ion secretion in proximal tubule exceeds that of carbonic acid dehydration at the concentrations of this acid found in blood. This suggestion is based on knowledge derived from in vitro kinetic studies concerning the CO 2 /HCO 3 buffer system and on the reactions thought to occur in the proximal tubule assuming reabsorption of bicarbonate via H ion secretion. The chapter reviews that in the disequilibrium pH in renal cortical tubules, besides a chemical disequilibrium within the bicarbonate/CO 2 buffer system leading to increased carbonic acid concentrations, CO 2 concentrations different from those of systemic arterial blood is a cause of lower pH values in proximal and distal tubules than in tubular fluid equilibrated with arterial pCO 2 . The magnitude of such pCO 2 values is studied by pCO 2 microelectrodes. The chapter presents the results, which indicates that the considerable permeability of tubular epithelium to CO 2 allows the establishment of only limited pCO 2 gradients of the order of 12 mmHg at the higher luminal bicarbonate levels. The data presented in the chapter also suggests that the pCO 2 of renal cortical interstitium and capillaries is not similar to that of peripheral blood.

Publisher Summary This chapter focuses on acid–base regulation in fishes. The maintenance of a constant pH in body fluids at a given temperature is one of the important tasks of the regulatory systems for homeostasis in animals. During normal steady-state conditions, there is a continuous production of surplus H+ or OH– ions, which are eliminated from the body fluids by the excretory organs of animals at the same rate as they are produced, such that pH in the body compartments is kept constant within narrow limits. Any description of the acid–base status of fish must focus on the pH value as a parameter of large significance for many biological functions. The pH in a body compartment can be affected by the addition or removal of H+ ions from the compartment fluid. This can result from changes in the concentration of the volatile anhydride of carbonic acid, CO2, or that of nonvolatile H+-dissociating substances (acids) and substances capable of transferring H+ ions into the nondissociated state (bases), induced by changed metabolic production. The chapter discusses the techniques used for the measurement of acid–base ion transfer. The acid–base status of fish is frequently stressed in addition to the endogenous steady-state load of surplus acid-base relevant ions by various endogenous and environmental factors. The chapter discusses the effect of some of these factors on the acid–base status and on ionic transfer processes.

This chapter presents the details of physiological aspects of control mechanisms of blood pH. The pH of blood, and hence extracellular fluid generally, must be maintained at a reasonably constant level. In general, mammals maintain the pH of the internal environment between 6.9 and 7.8. If, when hydrogen carbonate concentrations are changed, the partial pressure of carbon dioxide can be adjusted appropriately, then no change in pH should occur. Thus, addition of acid to the blood causes the loss of hydrogen carbonate. Changes in blood pH occur as a result of the ingestion of acid or alkali, as a result of metabolic disturbance, or as a result of a failure to match respiratory excretion of carbon dioxide to its metabolic production. The pH of the blood is controlled by adjusting the ratio of hydrogen carbonate concentration to that of carbon dioxide and carbonic acid. Changes in pH are apparent as changes in this ratio—control of pH consists of the restoration of the ratio by respiratory and renal adjustments. However, the first stage of control is by the purely physicochemical process of buffering, a process that permits the presence and transport of acid or alkali with relatively little pH change.

Publisher Summary This chapter describes the mixed carbonic anhydride method of peptide synthesis. Peptide bond formation by the mixed anhydride procedure involves two separate stages. The stages include activation of the carboxyl component, generation of a mixed anhydride of Nα -protected amino acid or peptide, and coupling with the amine component. The activation step is carried out by the addition of carbonic acid monoalkyl ester chloride to a cold solution of the carboxyl component anion in anhydrous organic solvent in the presence of a tertiary base. The activation time is the period between the addition of the alkyl chlorocarbonate and the addition of the amine component, once the mixed anhydride formation is complete. Peptide bond formation usually proceeds rapidly with liberation of carbon dioxide gas and a volatile alcohol as byproduct. This process is not very sensitive to the nature of the solvent, but it is prone to a few side reactions, of which only the formation of a second acylation product by attack of the amine component at the carbonic acid carbonyl is of practical concern.

Publisher Summary The fundamental mechanisms of urinary acidification are bicarbonate reabsorption and formation of titratable acidity, and it is generally conceded that hydrogen ion secretion by the tubular epithelium participates in both processes. However, it has repeatedly been proposed that an additional transport mechanism could exist for the bicarbonate anion in its ionic form. This chapter provides evidence that the buffer systems exist with widely varying permeance of their acid components, varying from practically impermeant components to systems with very permeant components that appear to maintain transepithelial concentration equilibrium (glycodiazine) and that this property determines the magnitude of the H + ion flux taken up by them in the tubular lumen. The H + ion source could be related to the process of recirculation of the diffusible acid, as proposed for carbonic acid. The acid formed in the lumen by H + ion secretion would diffuse into tubular cell and there could either dissociate, yielding an H + ion to the proton pump, or neutralize OH - ions formed by the water-splitting process of a redox pump.

Publisher Summary Chemolithotrophy is defined as the production of metabolically useful energy by the oxidation of inorganic compounds. Chemolithotrophy is coupled to a specific assimilatory physiology, the utilization of carbonic acid as the exclusive carbon source, as well as to exogenous organic matter. Attempts have been made to unify into a single concept, the aspects of physiology, energy generation, and carbon assimilation that are independent, in all possible combinations. This chapter deals with the roles of exogenous organic compounds in the physiology of chemolithotrophic bacteria. The chapter considers autotrophy and mixotrophy, the former refers to a completely inorganic medium or cells grown in such a medium and latter to a commingling of alternative modes of energy generation or carbon assimilation. Facultative autotrophs that oxidize either molecular hydrogen or reduced inorganic sulfur compound and obligate autotrophs in which energy is derived chemolithotrophically by the oxidation of ammonia or nitrite, reduced inorganic sulfur compounds, or ferrous ion are also presented.

Publisher Summary This chapter discusses the chemical reactions and the physiological mechanisms affecting the concentration of hydrogen ions in the various fluid compartments of the body. As acids are substances capable of delivering hydrogen ions, the concentration of hydrogen ions-[H + ] depends primarily on the amount of the various acids present in the body fluids. There are two principally different ways of regulating the acid–base balance. There is the metabolic way, dealing chiefly with the buffer processes of the homogeneous type, and there is the respiratory way, which deals chiefly with the buffer processes of the heterogeneous type. As an open system, the fish, like all other animals is defended twofold against changes of the acidity of its milieu interieur . The most important of the acids present in body is carbonic acid that is derived from carbon dioxide (CO 2 ), one of the major end products of metabolism. Hence, the equilibrium equations of carbonic acid and its reactions with the so-called buffer substances form the chemical basis of CO 2 transport and acid–base balance. The concentration of CO 2 and the chemical composition of the body fluids are therefore the principal factors governing acid–base balance. The former is controlled by ventilation, the latter by the action of various excretory mechanisms.

Publisher Summary This chapter discusses about di-(p-chlorophenyl)trichlorethane (DDT) that is usually determined by a biological method, for example, in the Drosophila assay. The quantitative determination of very small amounts of the insecticide by a halogen determination with a colorimetric, spectrographic, or polarographic method is either relatively unspecific or requires a large expenditure on apparatus. Very small amounts of DDT can be measured very accurately with carbonic anhydrase (CAH) by the inhibitory effect on the enzyme. Carbonic anhydrase catalyzes the hydration of carbon dioxide to carbonic acid. The DDT inhibition of CAH is not competitive. The binding sites for the insecticide include not only the catalytically active centre but also unspecific sites on the enzyme molecule. In addition to DDT, the samples frequently contain the γ-isomer of hexachlorocyclohexane (Lindane). This contact insecticide does not inhibit at the concentrations of DDT which occur in practice.

Publisher Summary This chapter discusses carbonic acid and its derivatives, a large and diverse group of compounds. Metacarbonic acid and its esters, such as carbon dioxide, esters of carbonic acid, anhydrides of primary esters of carbonic acid, mixed anhydrides of primary carbonates, and mono-carboxylic acids are also profiled with detailed information on general methods of preparation, properties, and typical reactions. Halides of carbonic acid, sulfur analogues of carbonic acid, and their derivatives, such as carbon oxysulfide and carbon disulfide, thiocarbonic acids and their halides, such as thiophosgene, amides, and related derivatives of carbonic acid, and the thiocarbonic acids are illustrated in a systematic manner. Special stress is evident in the discussion on urea and its derivatives, such as halogenoureas, ureides, and so on because of its commercial relevance as a fertilizer. Derivatives of iminodicarboxylic acid, such as biuret and nitrilotricarboxylic acid, sulfur analogues of carbamic acid, and hydrazino, azo, and azido derivatives of thiocarbonic acid are also emphasized in this chapter. Sulfur compounds of cyanogens, such as thiocyanic acid, cyanamide and its derivatives, and derivatives of carbodi-imide and orthocarbonic acid are also covered.