scholarly journals Spectrometric determinations of the effect of a neutral salt on the dissociation of acetic acid

1930 ◽  
Vol 130 (812) ◽  
pp. 1-16
Keyword(s):  
Acetic Acid ◽  
Methyl Orange ◽  
Preceding Paper ◽  
Ion Concentration ◽  
Neutral Salt ◽  
Apparent Dissociation Constant ◽  
Hydrogen Ion Concentration ◽  
K Value ◽  
Degree Of Dissociation ◽  
Colour Measurements

This paper gives an account of an extension of the work contained in the preceding paper (Sidgwick, Worboys and Woodward). For the first part the simple photoelectric colorimeter described in that paper was used. For the Second part a new type of flicker photometer was constructed. The principle of both instruments is the same, and has been given in the previous paper together with the theory of the colour changes of methyl orange, the indicator used throughout. The colour measurements allow us to determine the value of the apparent dissociation constant K of methyl orange in presence of various concentrations of natural salt. At a given salt concentration therefore the use of the appropriate K value will enable us to calculate the true hydrogen ion concentration of such a solution from its colour. In this way the degree of dissociation of acetic acid has been investigated in presence of different amounts of the neutral salt potassium bromide.

Studies on soil reaction: III. The determination of the hydrogenion concentration of soil suspensions by means of the hydrogen electrode

1925 ◽  
Vol 15 (2) ◽  
pp. 201-221 ◽  
Author(s):  
Edward M. Crowther
Keyword(s):  
Dilution Effect ◽  
Ion Concentration ◽  
Soil Reaction ◽  
Neutral Salt ◽  
Alkaline Soils ◽  
Hydrogen Electrode ◽  
Hydrogen Ion Concentration ◽  
Base Exchange ◽  
Buffer Action ◽  
Hydrogenion Concentration

A hydrogen electrode apparatus for soils is described. Similar or adjacent soils may show considerable differences inpH value, with no changes in their degrees of buffer action, as shown in titration curves with lime water. In such cases the conventional “lime requirements” are correlated with thepH values, but no such relation holds in dissimilar soils. ThepH value of a soil suspension is intimately connected with the nature and amount of the cations present. Neutral salts markedly increase the hydrogen ion concentration of both acid and slightly alkaline soils. Sodium salts, including the hydroxide, give lower hydrogenion concentrations than the corresponding potassium or calcium salts, and chlorides give lowerpH values than sulphates. The degree of buffer action (slope of titration curve) is unaffected by the addition of a neutral salt. Previous extraction of a soil with water causes a considerable increase i n thepH value of its suspensions. A number of soils showed a regular increase of about 0·1 inpH. value for twofold dilution. The “salt effect” and “dilution” effect appear to be of the same type. It is recommended that the soil-water ratio of 1:5 be generally adopted. The indicator methyl red gives erroneouspH values in turbid soil suspensions owing to the absorption of the red form, which is apparently a cation capable of undergoing “base exchange” with the soil.

scholarly journals THE EFFECT OF VARIOUS ACIDS ON THE DIGESTION OF PROTEINS BY PEPSIN

1919 ◽  
Vol 1 (6) ◽  
pp. 607-612 ◽  
Author(s):  
J. H. Northrop
Keyword(s):  
Acetic Acid ◽  
The State ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Pepsin Digestion ◽  
Marked Influence ◽  
Egg Albumin ◽  
Blood Albumin ◽  
Salt Action

1. At equal hydrogen ion concentration the rate of pepsin digestion of gelatin, egg albumin, blood albumin, casein, and edestin is the same in solutions of hydrochloric, nitric, sulfuric, oxalic, citric, and phosphoric acids. Acetic acid diminishes the rate of digestion of all the proteins except gelatin. 2. There is no evidence of antagonistic salt action in the effect of acids on the pepsin digestion of proteins. 3. The state of aggregation of the protein, i.e. whether in solution or not, and the viscosity of the solution have no marked influence on the rate of digestion of the protein.

Di Brom Thymol Sulhpone Phthalein as a Reagent for Determining the Hydrogen Ion Concentration of Living Cells

1922 ◽  
Vol 12 (4) ◽  
pp. 781-784 ◽  
Author(s):  
W. R. G. Atkins
Keyword(s):  
Sea Water ◽  
Living Cells ◽  
Marine Organisms ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Toxic Action ◽  
Thymol Blue ◽  
Neutral Salt ◽  
Dilute Solution ◽  
Hydrogen Ion Concentration

1. Brom thymol blue may be used in dilute solution for ascertaining the hydrogen ion concentration of certain marine organisms. It penetrates slowly, but the stained portions remain actively motile, so its toxic action does not appear to be great at the dilutions found serviceable.2. The animals studied gave values from pH6·2 to about pH7·5, though possibly the more alkaline end of the range may be pathological. About pH0·2 should be subtracted from these figures for neutral salt error. The sea water used was initially at pH8·2, corrected.

scholarly journals Colorimetric investigations of indicators in presence of neutral salts

1930 ◽  
Vol 129 (811) ◽  
pp. 537-549 ◽  
Keyword(s):  
Wave Length ◽  
Colorimetric Method ◽  
Photoelectric Effect ◽  
Null Point ◽  
Ion Concentration ◽  
Neutral Salt ◽  
Hydrogen Ion Concentration ◽  
Other Substances ◽  
Colorimetric Measurements ◽  
Optical Wedge

It is known that the colour exhibited by a definite concentration of an indicator in a solution of given hydrogen ion concentration is changed by the presence of neutral salts. As is shown in the present paper, the evaluation of this neutral salt effect by colorimetric measurements can be made to furnish information as to the dissociation of the indicator in slat solutions, and further, the knowledge so obtained can be used to investigate the dissociation of other substances in presence of neutral salts. The colorimetric method employed was similar to that of v. Halban and Geigel, making use of the photoelectric effect. The advantages of this over the photographic method have recently been discussed by v. Halban and Eisenbrand. Our apparatus enabled the absorption of a solution to be measured against that of an optical wedge, so that the photoelectric effect entered only as a null-point observation. I. The Colorimeter . A parallel beam of white light passes through a glass cell containing the solution to be measured, and then through a glass prism. The light of a narrow wave-length band is admitted to the photoelectric cell through a slit, before which an optical wedge is placed. The photoelectric current passes to earth through a fixed resistance, and gives a steady deflection to the needle of a sensitive electrometer. The cell and solution are then removed, and the wedge is shifted so as to absorb more light, until the original electrometer deflection is restored. The absorption corresponding to the wedge shift is then equal to that of the cell and solution.

scholarly journals AMPHOTERIC COLLOIDS

1918 ◽  
Vol 1 (1) ◽  
pp. 39-60 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Physical Properties ◽  
Osmotic Pressure ◽  
Isoelectric Point ◽  
Alkali Treatment ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Neutral Salt ◽  
Sharp Drop ◽  
Hydrogen Ion Concentration ◽  
Alkaline Side

1. It has been shown in this paper that while non-ionized gelatin may exist in gelatin solutions on both sides of the isoelectric point (which lies for gelatin at a hydrogen ion concentration of CH = 2.10–5 or pH = 4.7), gelatin, when it ionizes, can only exist as an anion on the less acid side of its isoelectric point (pH > 4.7), as a cation only on the more acid side of its isoelectric point (pH < 4.7). At the isoelectric point gelatin can dissociate practically neither as anion nor as cation. 2. When gelatin has been transformed into sodium gelatinate by treating it for some time with M/32 NaOH, and when it is subsequently treated with HCl, the gelatin shows on the more acid side of the isoelectric point effects of the acid treatment only; while the effects of the alkali treatment disappear completely, showing that the negative gelatin ions formed by the previous treatment with alkali can no longer exist in a solution with a pH < 4.7. When gelatin is first treated with acid and afterwards with alkali on the alkaline side of the isoelectric point only the effects of the alkali treatment are noticeable. 3. On the acid side of the isoelectric point amphoteric electrolytes can only combine with the anions of neutral salts, on the less acid side of their isoelectric point only with cations; and at the isoelectric point neither with the anion nor cation of a neutral salt. This harmonizes with the statement made in the first paragraph, and the experimental results on the effect of neutral salts on gelatin published in the writer's previous papers. 4. The reason for this influence of the hydrogen ion concentration on the stability of the two forms of ionization possible for an amphoteric electrolyte is at present unknown. We might think of the possibility of changes in the configuration or constitution of the gelatin molecule whereby ionized gelatin can exist only as an anion on the alkaline side and as a cation on the acid side of its isoelectric point. 5. The literature of colloid chemistry contains numerous statements which if true would mean that the anions of neutral salts act on gelatin on the alkaline side of the isoelectric point, e.g. the alleged effect of the Hofmeister series of anions on the swelling and osmotic pressure of common gelatin in neutral solutions, and the statement that both ions of a neutral salt influence a protein simultaneously. The writer has shown in previous publications that these statements are contrary to fact and based on erroneous methods of work. Our present paper shows that these claims of colloid chemists are also theoretically impossible. 6. In addition to other physical properties the conductivity of gelatin previously treated with acids has been investigated and plotted, and it was found that this conductivity is a minimum in the region of the isoelectric point, thus confirming the conclusion that gelatin can apparently not exist in ionized condition at that point. The conductivity rises on either side of the isoelectric point, but not symmetrically for reasons given in the paper. It is shown that the curves for osmotic pressure, viscosity, swelling, and alcohol number run parallel to the curve of the conductivity of gelatin when the gelatin has been treated with acid, supporting the view that these physical properties are in this case mainly or exclusively a function of the degree of ionization of the gelatin or gelatin salt formed. It is pointed out, however, that certain constitutional factors, e.g. the valency of the ion in combination with the gelatin, may alter the physical properties of the gelatin (osmotic pressure, etc.) without apparently altering its conductivity. This point is still under investigation and will be further discussed in a following publication. 7. It is shown that the isoelectric point of an amphoteric electrolyte is not only a point where the physical properties of an ampholyte experience a sharp drop and become a minimum, but that it is also a turning point for the mode of chemical reactions of the ampholyte. It may turn out that this chemical influence of the isoelectric point upon life phenomena overshadows its physical influence. 8. These experiments suggest that the theory of amphoteric colloids is in its general features identical with the theory of inorganic hydroxides (e.g. aluminum hydroxide), whose behavior is adequately understood on the basis of the laws of general chemistry.

VISCOSITY OF GLUTEN DISPERSED IN ALKALI, ACID AND NEUTRAL SOLVENTS

1935 ◽  
Vol 12 (1) ◽  
pp. 63-81 ◽  
Author(s):  
R. C. Rose ◽  
W. H. Cook
Keyword(s):  
Acetic Acid ◽  
Sodium Hydroxide ◽  
Protein Quality ◽  
Sodium Salicylate ◽  
Ion Concentration ◽  
Salting Out ◽  
Hydrogen Ion Concentration ◽  
Effective Particle ◽  
Ph Range

The viscosity of gluten dispersed in urea and sodium salicylate was higher, and showed a greater increase with increasing protein concentration, than that of dispersions of the same age and concentration, in sodium hydroxide and acetic acid solutions. Calculations, based on these measurements, indicated that the effective particle size is larger in the former pair of solvents. In urea solutions the viscosity of dilute gluten dispersions was independent of the hydrogen ion concentration between pH 6.1 and 9.2, and within this range the system was stable. Beyond this pH range the viscosity at first increased, but the system was unstable as shown by a subsequent rapid decrease in viscosity with time.Dilute dispersions in sodium hydroxide, urea and sodium salicylate solutions decreased in viscosity at first, whereas the viscosity of dispersions in acetic acid decreased continuously. Some evidence was obtained of coagulation in concentrated dispersions in the neutral solvents at 0 °C. and 25 °C.The character of the precipitate obtained by salting out dispersions in each of the four solvents after storage at 25 °C. indicated that the neutral solvents alter the gluten less than alkali or acid. This conclusion is supported by the fact that glutens obtained from flours of different protein quality had essentially the same viscosity when dispersed in alkali or acid, but in the neutral solvents exhibited markedly different viscosities which were partially correlated with the quality of the gluten.

scholarly journals DONNAN EQUILIBRIUM AND THE PHYSICAL PROPERTIES OF PROTEINS

1921 ◽  
Vol 3 (5) ◽  
pp. 667-690 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Osmotic Pressure ◽  
Chloride Solution ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Neutral Salt ◽  
Hydrogen Ion Concentration ◽  
Monovalent Anion ◽  
Donnan Equilibrium ◽  
The Difference ◽  
Fair Degree

1. It is shown that a neutral salt depresses the potential difference which exists at the point of equilibrium between a gelatin chloride solution contained in a collodion bag and an outside aqueous solution (without gelatin). The depressing effect of a neutral salt on the P.D. is similar to the depression of the osmotic pressure of the gelatin chloride solution by the same salt. 2. It is shown that this depression of the P.D. by the salt can be calculated with a fair degree of accuracy on the basis of Nernst's logarithmic formula on the assumption that the P.D. which exists at the point of equilibrium is due to the difference of the hydrogen ion concentration on the opposite sides of the membrane. 3. Since this difference of hydrogen ion concentration on both sides of the membrane is due to Donnan's membrane equilibrium this latter equilibrium must be the cause of the P.D. 4. A definite P.D. exists also between a solid block of gelatin chloride and the surrounding aqueous solution at the point of equilibrium and this P.D. is depressed in a similar way as the swelling of the gelatin chloride by the addition of neutral salts. It is shown that the P.D. can be calculated from the difference in the hydrogen ion concentration inside and outside the block of gelatin at equilibrium. 5. The influence of the hydrogen ion concentration on the P.D. of a gelatin chloride solution is similar to that of the hydrogen ion concentration on the osmotic pressure, swelling, and viscosity of gelatin solutions, and the same is true for the influence of the valency of the anion with which the gelatin is in combination. It is shown that in all these cases the P.D. which exists at equilibrium can be calculated with a fair degree of accuracy from the difference of the pH inside and outside the gelatin solution on the basis of Nernst's logarithmic formula by assuming that the difference in the concentration of hydrogen ions on both sides of the membrane determines the P.D. 6. The P.D. which exists at the boundary of a gelatin chloride solution and water at the point of equilibrium can also be calculated with a fair degree of accuracy by Nernst's logarithmic formula from the value pCl outside minus pCl inside. This proves that the equation x2 = y ( y + z) is the correct expression for the Donnan membrane equilibrium when solutions of protein-acid salts with monovalent anion are separated by a collodion membrane from water. In this equation x is the concentration of the H ion (and the monovalent anion) in the water, y the concentration of the H ion and the monovalent anion of the free acid in the gelatin solution, and z the concentration of the anion in combination with the protein. 7. The similarity between the variation of P.D. and the variation of the osmotic pressure, swelling, and viscosity of gelatin, and the fact that the Donnan equilibrium determines the variation in P.D. raise the question whether or not the variations of the osmotic pressure, swelling, and viscosity are also determined by the Donnan equilibrium.

XL—On the Binding of Acetic Acid by Proteins

1969 ◽  
Vol 70 (3) ◽  
pp. 228-232
Author(s):  
J. K. Candlish ◽  
G. R. Tristram
Keyword(s):  
Acetic Acid ◽  
Citric Acid ◽  
Organic Acids ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Peptide Bonds ◽  
Hydrogen Ion Concentration ◽  
Mineral Acids

Organic acids are working solvents for a number of proteins, notably the collagens. The mechanism of solubilization can be assumed, as a first hypothesis, to consist of a weakening of salt bonds such that chain-chain interactions are lessened and dispersion can occur. However, this cannot be exclusively true since, in the case of the collagen, it has been pointed out (Gustavson 1956) that this protein is soluble in acetic acid (pK=4·76 at 25°C.) and citric acid (pK1 = 3·13; pK2=476; pK3=6·39, at 25°) but not in hydrochloric or mineral acids of equivalent or greater hydrogen ion concentration. The hydrogen ion is thus not the dominant solubilising factor. The same author suggested that the unionized organic acids were bound by peptide bonds of proteins in such a way as to wedge apart the associated chains.

scholarly journals THE ORIGIN OF THE POTENTIAL DIFFERENCES RESPONSIBLE FOR ANOMALOUS OSMOSIS

1921 ◽  
Vol 4 (2) ◽  
pp. 213-226 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Salt Solution ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Neutral Salt ◽  
Hydrogen Ion Concentration ◽  
Hno3 Solution ◽  
Donnan Equilibrium ◽  
Double Origin ◽  
Concentration Cells ◽  
As If

1. Collodion bags coated with gelatin on the inside were filled with a M/256 solution of neutral salt (e.g., NaCl, CaCl2, CeCl3, or Na2SO4) made up in various concentrations of HNO3 (varying from N/50,000 to N/100). Each collodion bag was put into an HNO3 solution of the same concentration as that inside the bag but containing no salt. In this case water diffuses from the outside solution (containing no salt) into the inside solution (containing the salt) with a relative initial velocity which can be expressed by the following rules: (a) Water diffuses into the salt solution as if the particles of water were negatively charged and as if they were attracted by the cation and repelled by the anion of the salt with a force increasing with the valency of the ion. (b) The initial rate of the diffusion of water is a minimum at the hydrogen ion concentration of about N/50,000 HCl (pH 4.7, which is the point at which gelatin is not ionized), rises with increasing hydrogen ion concentration until it reaches a maximum and then diminishes again with a further rise in the initial hydrogen ion concentration. 2. The potential differences between the salt solution and the outside solution (originally free from salt) were measured after the diffusion had been going on for 1 hour; and when these values were plotted as ordinates over the original pH as abscissae, the curves obtained were found to be similar to the osmotic rate curves. This confirms the view expressed by Girard) Bernstein, Bartell, and Freundlich that these cases of anomalous osmosis are in reality cases of electrical endosmose where the driving force is a P.D. between the opposite sides of the membrane. 3. The question arose as to the origin of these P. D. and it was found that the P.D. has apparently a double origin. Certain features of the P.D. curve, such as the rise and fall with varying pH, seem to be the consequence of a Donnan equilibrium which leads to some of the free HNO3 being forced from the solution containing salt into the outside solution containing no (or less) salt. This difference of the concentration of HNO3, on the opposite sides of the membrane leads to a P.D. which in conformity with Nernst's theory of concentration cells should be equal to 58 x (pH inside minus pH outside) millivolts at 18°C. The curves of the values of (pH inside minus pH outside) when plotted as ordinates over the original pH as abscissae lead to curves resembling those for the P. D. in regard to location of minimum and maximum. 4. A second source of the P.D. seems to be diffusion potentials, which exist even if no membranes are present and which seem to be responsible for the fact that the rate of diffusion of negatively charged water into the salt solution increases with the valency of the cation and diminishes with the valency of the anion of the salt. 5. The experiments suggest the possibility that the establishment of a Donnan equilibrium between membrane and solution is one of the factors determining the Helmholtzian electrical double layer, at least in the conditions of our experiments.

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