Ionic Equilibria and pH

2009 ◽  
Author(s):  
Christopher O. Oriakhi
Keyword(s):  
Pure Water ◽  
Weak Acid ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ions ◽  
Hydrogen Ion Concentration ◽  
M 10 ◽  
Ionic Equilibria ◽  
Hydrated Protons ◽  
Dilute Aqueous Solution

Water is a weak acid. At 25°C, pure water ionizes to form a hydrogen ion and a hydroxide ion: H2O ⇋ H+ + OH− Hydration of the proton (hydrogen ion) to form hydroxonium ion is ignored here for simplicity. This equilibrium lies mainly to the left; that is, the ionization happens only to a slight extent. We know that 1 L of pure water contains 55.6 mol. Of this, only 10−7 mol actually ionizes into equal amounts of [H+] and [OH−], i.e., [H+] = [OH−] = 10−7M Because these concentrations are equal, pure water is neither acidic nor basic. A solution is acidic if it contains more hydrogen ions than hydroxide ions. Similarly, a solution is basic if it contains more hydroxide ions than hydrogen ions. Acidity is defined as the concentration of hydrated protons (hydrogen ions); basicity is the concentration of hydroxide ions. Pure water ionizes at 25°C to produce 10−7 M of [H+] and 10−7 M of [OH−]. The product Kw = [H+]×[OH−] = 10−7 M×10−7 M= 10−14 M is known as the ionic product of water. Note that this is simply the equilibrium expression for the dissociation of water. This equation holds for any dilute aqueous solution of acid, base, and salt. The pH of a solution is defined as the negative logarithm of the molar concentration of hydrogen ions. The lower the pH, the greater the acidity of the solution. Mathematically: pH=−log10[ H+] or −log10[H3O+] This can also be written as: pH = log10 1/[H+] or log10 1/[H3O+] Taking the antilogarithm of both sides and rearranging gives: [H+] = 10−pH This equation can be used to calculate the hydrogen ion concentration when the pH of the solution is known.

scholarly journals The Hydrogen Ion Concentration in the Gut of certain Lamellibranchs and Gastropods

1925 ◽  
Vol 13 (4) ◽  
pp. 938-952 ◽  
Author(s):  
O. M. Yonge
Keyword(s):  
Mantle Cavity ◽  
Mya Arenaria ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Pecten Maximus ◽  
Hydrogen Ions ◽  
Acid Media ◽  
Hydrogen Ion Concentration ◽  
Acid Reaction ◽  
Acid Region

1. In the Lamellibranchs, as typified by Pecten maximus, Mya arenaria and Ensis siliqua, the entire, gut has an acid reaction, the stomach being the most acid region and the pH rising along the mid-gut and rectum.2. The origin of the acidity of the gut lies in the style. This has a low pH (5·4 in Pecten and Mytilus, 4·6 in Ensis and 4·45 in Mya), and, after it has been artificially extracted from Mya or induced to disappear, by keeping the animals under abnormal conditions, in Mytilus, Tapes and Pecten, the pH of the stomach invariably rises (by as much as 0·825 in Mya and 0·72 in Tapes), although the pH in the mantle cavity has fallen.3. The style, which dissolves rapidly in alkaline or weakly acid media, is not dissolved in fluids below a certain pH—4·4 for Ensis, 4·2 for Mya, 3·6 for Pecten and Mytilus.4. The style is never absent, even though animals are starved, so long as they are kept under otherwise healthy conditions. The disappearance of the style under abnormal conditions is probably due to a lowering of the vital activities, which include the secretion of the style substance, and the consequent dissolution of the style by the less acid contents of the stomach.5. The style is only maintained as a result of a balance between the rate of its secretion and the rate of its dissolution.6. There is a well-marked correlation between the tolerance of the presence of hydrogen ions possessed by the cilia from the various regions of the gut and the degree of acidity of the fluid with which they are normally surrounded.7. The pH of the gut in five Gastropods has been investigated. The fore-gut and stomach have invariably the lowest pH.8. This acidity may be caused by the salivary glands (Patella and Buccinum), the digestive gland (Doris and Aplysia), or the style (Crepidula).9. The mid-gut and rectum have a high pH, except in Doris, where there is little secretion of mucus, the gut being free and muscular.10. The style of Orepidula has similar properties to those of the Lamellibranchs. It has a pH of 5·8, and is not dissolved in fluid of pH 3·6 or lower.11. The cilia from the gut of Buccinum and Doris can function in a pH of 5·0, but there is little difference in the toleration of the various cilia to the presence of hydrogen ions.

Memoirs: The Spermatheca of Loligo Vulgaris. I. Structure of the Spermatheca and Function of its Unicellular Glands

1938 ◽  
Vol s2-80 (320) ◽  
pp. 593-599
Author(s):  
G. J. van OORDT
Keyword(s):  
Sea Water ◽  
Goblet Cells ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ions ◽  
Hydrogen Ion Concentration ◽  
Loligo Vulgaris ◽  
And Function

The structure of the spermatheca of Loligo vulgaris is described; it lies on the inner wall of the buccal membrane and within it large quantities of inactive spermatozoa are stored. This inactivity of the spermatozoa within the spermatheea is attributed to the effect of the secretion of the goblet-cells, situated as unicellular glands on the inner wall of the spermatheca. Inactive spermatozoa from the spermatheca become very active in sea-water, but are immobilized again after a few moments' contact with the pulp of the spermatheca contents. The hydrogen-ion concentration of the spermatheca contents is approximately 6.06; and, since spermatozoa become inactive in sea-water, the hydrogen-ion concentration of which is increased to this level, it seems probable that the inactivity of the spermatozoa within the spermatheca is due to the presence of hydrogen-ions. The spermatheca is functionally comparable to the mammalian epididymis.

A physiological approach to acid–base disorders: The roles of ion transport and body fluid compartments

2020 ◽  
pp. 2182-2198
Author(s):  
Julian Seifter
Keyword(s):  
Metabolic Acidosis ◽  
Gas Analysis ◽  
Hydrogen Ion ◽  
Anion Gap ◽  
Ion Concentration ◽  
Hydrogen Ions ◽  
Acid Base ◽  
Hydrogen Ion Concentration ◽  
Arterial Blood Gas ◽  
Fluid Compartments

The normal pH of human extracellular fluid is maintained within the range of 7.35 to 7.45. The four main types of acid–base disorders can be defined by the relationship between the three variables, pH, Pco2, and HCO3 –. Respiratory disturbances begin with an increase or decrease in pulmonary carbon dioxide clearance which—through a shift in the equilibrium between CO2, H2O, and HCO3 –—favours a decreased hydrogen ion concentration (respiratory alkalosis) or an increased hydrogen ion concentration (respiratory acidosis) respectively. Metabolic acidosis may result when hydrogen ions are added with a nonbicarbonate anion, A−, in the form of HA, in which case bicarbonate is consumed, or when bicarbonate is removed as the sodium or potassium salt, increasing hydrogen ion concentration. Metabolic alkalosis is caused by removal of hydrogen ions or addition of bicarbonate. Laboratory tests usually performed in pursuit of diagnosis, aside from arterial blood gas analysis, include a basic metabolic profile with electrolytes (sodium, potassium, chloride, bicarbonate), blood urea nitrogen, and creatinine. Calculation of the serum anion gap, which is determined by subtracting the sum of chloride and bicarbonate from the serum sodium concentration, is useful. The normal value is 10 to 12 mEq/litre. An elevated value is diagnostic of metabolic acidosis, helpful in the differential diagnosis of the specific metabolic acidosis, and useful in determining the presence of a mixed metabolic disturbance. Acid–base disorders can be associated with (1) transport processes across epithelial cells lining transcellular spaces in the kidney, gastrointestinal tract, and skin; (2) transport of acid anions from intracellular to extracellular spaces—anion gap acidosis; and (3) intake.

scholarly journals SOME CONSEQUENCES OF THE THEORY OF MEMBRANE EQUILIBRIA

1925 ◽  
Vol 9 (1) ◽  
pp. 97-109 ◽  
Author(s):  
David I. Hitchcock
Keyword(s):  
Membrane Potential ◽  
Osmotic Pressure ◽  
Ionization Constant ◽  
Weak Acid ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Weak Base ◽  
Acid Base ◽  
Hydrogen Ion Concentration ◽  
Pass Through

In applying Donnan's theory of membrane equilibria to systems where the non-diffusible ion is furnished by a weak acid, base, or ampholyte, certain new relations have been derived. Equations have been deduced which give the ion ratio and the apparent osmotic pressure as functions of the concentration and ionization constant of the weak electrolyte, and of the hydrogen ion concentration in its solution. The conditions for maximum values of these two properties have been formulated. It is pointed out that the progressive addition of acid to a system containing a non-diffusible weak base should not cause the value of the membrane potential to rise, pass through a maximum, and fall, but should only cause it to diminish. It is shown that the theory predicts slight differences in the effect of salts on the ion ratio in such systems, the effect increasing with the valence of the cation.

scholarly journals THE REVERSAL OF THE SIGN OF THE CHARGE OF MEMBRANES BY HYDROGEN IONS

1920 ◽  
Vol 2 (5) ◽  
pp. 577-594 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Thin Film ◽  
Isoelectric Point ◽  
Positive Charge ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ions ◽  
Acid Salt ◽  
Hydrogen Ion Concentration ◽  
Protein Film

1. It had been shown in previous papers that when a collodion membrane has been treated with a protein the membrane assumes a positive charge when the hydrogen ion concentration of the solution with which it is in contact exceeds a certain limit. It is pointed out in this paper that by treating the collodion membrane with a protein (e.g. oxyhemoglobin) a thin film of protein adheres to the membrane and that the positive charge of the membrane must therefore be localized in this protein film. 2. It is further shown in this paper that the hydrogen ion concentration, at which the reversal in the sign of the charge of a collodion membrane treated with a protein occurs, varies in the same sense as the isoelectric point of the protein, with which the membrane has been treated, and is always slightly higher than that of the isoelectric point of the protein used. 3. The critical hydrogen ion concentration required for the reversal seems to be, therefore, that concentration where enough of the protein lining of the membrane is converted into a protein-acid salt (e.g. gelatin nitrate) capable of ionizing into a positive protein ion (e.g. gelatin) and the anion of the acid used (e.g. NO3).

The Formation of 3-Phenyl-2-thiohydantoins from Phenylthiocarbamyl Amino Acids

1963 ◽  
Vol 16 (3) ◽  
pp. 411 ◽  
Author(s):  
D Ilse ◽  
P Edman
Keyword(s):  
Amino Acids ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ions ◽  
Hydrogen Ion Concentration ◽  
First Order ◽  
First Order Kinetics ◽  
Kinetics Of ◽  
Degradation Of Peptides

In an attempt to extend the application of the phenylisothiocyanate degradation of peptides it was found necessary to study the kinetics of the conversion of phenylthiocarbamyl amino acids into phenylthiohydantoins. The conversion was found to obey first-order kinetics and to be catalyzed by hydrogen ions. A set of conditions with regard to time, hydrogen ion concentration and temperature was found, which allowed the quantitative or near quantitative conversion of all phenylthiocarbamyl amino acids into phenylthiohydantoins with the only exception of the phenylthiohydantoin of serine, which was returned in a yield of 20%.

scholarly journals Ionic Blockage of Sodium Channels in Nerve

1973 ◽  
Vol 61 (6) ◽  
pp. 687-708 ◽  
Author(s):  
Ann M. Woodhull
Keyword(s):  
Sodium Channel ◽  
Sodium Channels ◽  
Voltage Dependence ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ions ◽  
Sodium Permeability ◽  
Bathing Medium ◽  
Hydrogen Ion Concentration ◽  
Voltage Dependent

Increasing the hydrogen ion concentration of the bathing medium reversibly depresses the sodium permeability of voltage-clamped frog nerves. The depression depends on membrane voltage: changing from pH 7 to pH 5 causes a 60% reduction in sodium permeability at +20 mV, but only a 20% reduction at +180 mV. This voltage-dependent block of sodium channels by hydrogen ions is explained by assuming that hydrogen ions enter the open sodium channel and bind there, preventing sodium ion passage. The voltage dependence arises because the binding site is assumed to lie far enough across the membrane for bound ions to be affected by part of the potential difference across the membrane. Equations are derived for the general case where the blocking ion enters the channel from either side of the membrane. For H+ ion blockage, a simpler model, in which H+ enters the channel only from the bathing medium, is found to be sufficient. The dissociation constant of H+ ions from the channel site, 3.9 x 10-6 M (pKa 5.4), is like that of a carboxylic acid. From the voltage dependence of the block, this acid site is about one-quarter of the way across the membrane potential from the outside. In addition to blocking as described by the model, hydrogen ions also shift the responses of sodium channel "gates" to voltage, probably by altering the surface potential of the nerve. Evidence for voltage-dependent blockage by calcium ions is also presented.

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