Buffer value

The buffer values for the NBS reference pH buffer solutions are given below ... 

For the secondary pH reference standards, the buffer value is 0.070 for potassium tetroxalate and 0.09 for calcium hydroxide. 

Values based on the conventional activity pH scale as defined by the National Bureau of Standards (U.S.) and pertain to a temperature of 25°C [Ref Bower and Bates, J. Research Natl. Bur. Standards U.S., 55 197 (1955) and Bates and Bower, Anal. Chem., 28 1322 (1956)]. Buffer value is denoted by column headed /3. 

Pufferung,/. buffering cushioning. Puffer-wert, m. buffer value, -wirkung, /. buffer action or effect. 

The detritiation of [3H]-2,4,6-trimethoxybenzene by aqueous perchloric acid was also studied, the second-order rate coefficients (107/c2) being determined as 5.44, 62.0, and 190 at 0, 24.6, and 36.8 °C, respectively, whilst with phosphate buffers, values were 3.75, 13.8, and 42.1 at 24.6, 39.9, and 55.4 °C, respectively. The summarised kinetic parameters for these studies are given in Table 134, and notable among the values are the more negative entropies of activation obtained in catalysis by the more negative acids. This has been rationalised in terms of proton transfer... 

Keyboard sixteen push-buttons for entry of data and instructions for manual or automatic calibration, based on the three National Bureau of Standards (NBS) buffers of pH 4, 7 and 9, whose values as a function of temperature have been permanently and separately stored to three decimal places and at intervals of 0.1° C. Hence there is no need to enter pH values, as the electrode automatically identifies the buffer in use and the apparatus immediately retrieves and displays the temperature-adjusted buffer value the isopotential adjustment is defaulted to pH 7.000. 

The competition reaction is characterized by one buffer value (bidistilled water) and various concentrations of non-labeled fibrinogen or test compound. 

Buffer Value H2 Pipet 200 pL of MES Buffer with Brij 35 and Sodium Chloride into a 10-mL test tube in the 30° water bath. Add 200 pL of a-Acetolactate Substrate, mix, and immediately replace the test tube into the water bath. 

The deposition of greenalite and its interrelationships with siderite are controlled by reactions (2.16) and (2.17), considered earlier. The line separating the field of deposition of Sid and Gree (Fig. 24) in the first approximation characterizes the conditions of joint deposition of Fe-Mg carbonates and silicates of variable composition. From the diagram it is seen that as the content of Fe in solution decreases and, apparently, the magnesium content of the minerals deposited increases somewhat, the buffer value of also decreases several times from 7- 10 to (l-2)- 10 bar. Inasmuch as in most Precambrian BIF magnesian silicates occur relatively rarely (the finding of talc in the unoxidized oxide facies of the BIF of the... 

The buffer value (p) is defined as the amount of base required to cause a change in pH of one unit. The buffer value of the bicarbonate buffer in plasma is 55.6 mmol/L. Derivation of this value is obtained by taking partial differentials of the Henderson-Hasselbalch equation, which is presented in detail in the second edition of this textbook. ... 

At a plasma pH of 7.4, the ratio c HP047cH2P04 is 4/1 (plC = 6.8). The total concentration of this buffer in both erythrocytes and plasma is less than that of other major buffer systems, accounting for only about 5% of the nonbicarbonate buffer value of plasma. Organic phosphate, however, in the form of 2,3-diphosphoglycerate (present in erythrocytes in a concentration of about 4.5 mmol/L), accounts for about 16% of the nonbicarbonate buffer value of erythrocyte fluid. 

Plasma Protein Buffer System and Plasma Base Excess The buffer value (p) of the nonbicarbonate buffers of plasma is about 7.7 mmol/L at pH 7.40 and a normal plasma protein concentration of 72 g/L. Proteins, especially albumin, account for the greatest portion (95%) of the nonbicarbonate buffer value of the plasma. The most important buffer groups of proteins in the physiological pH range are the imidazole groups of histidines (pimolecule contains 16 histidines. 

As in plasma, CO2 equilibration of whole blood depends on the buffer value of nonbicarbonate buffers. Thus CO2 equilibration in whole blood is dependent on hemoglobin concentration and also on pH and oxygenation status. It is possible to derive an approximate equation for whole blood CO2 equilibration and calculation of whole blood base excess as follows ... 

Van Si.YKii, D. D. 1922. On the measurement of buffer values and on the relationship of buffer values to the dissociation constant of the buffer and the concentration and reaction of the buffer solution. J. Biol. Chem. 52 525-70. 

It is important for different purposes to be able to express quantitatively the buffer capacity of a liquid. In this connection, a paper by Donald D. van Slyke "On the Measurements of Buffer-values and on the Relationship of Buffer-value to the Dissociation Constant of the Buffer and the Concentration and Reaction of the Buffer Solution will be summarized briefly in the following paragraphs. 

As a measure of the relative effectiveness of buffer solutions in maintaining the pH constant when small amounts of add or base are added, Van Slyke85 has suggested the use of a quantity called the buffer value defined by... 

A formula for computing the buffer value may be obtained as follows. If to a liter of a solution of a weak acid of concentration C, B equivalents of a strong base are added, the stoichiometric concentrations of add and its salt will be respectively, (C B) and B. 

On differentiation, equation (32) yields for the buffer value, rfB/rfpH, the relation... 

The real roots of this cubic equation correspond to maxima or minima of buffer value, dB/2.3d(pH). The poteutiometric end point of the titration will, of course, correspond to a minimum in the buffer value. It is possible with the aid of this equation to predict the relation between KaC and Kw at which such minima appear in a titration curve. 

McGraw-Hill, 1997, and even some remnants of my Spreadsheet Workbook for Quantitative Chemical Analysis, McGraw-Hill, 1992. This is partially because I have retained some of the didactic innovations introduced in these earlier texts, such as an emphasis on the progress of a titration rather than on the traditional titration curve, the use of buffer strength rather than buffer value, and the use of the abbreviations h and A in the description of electrochemical equilibria. However, the present text exploits the power of Excel to go far beyond what was possible in those earlier books. 

FIGURE 9. Purified PSPBP activity from Acanthocardia tuberculatum foot in 4.0-10.0 pH range using a mixture of different buffers. Values are given as means of three separate experiments. For experimental conditions, see Materials and Methods. 

The dependence on pH is very marked. Within the above pH range the oxidation rate increases by about 100 times for a pH increase of one unit. In a more detailed description the effects of temperature and light are also taken into account. The positive or negative effect of different anions depends on the stability of their complexes with Fe(II) or Fe(III). If more stable complexes with Fe(III) are formed then the oxidation rate increases, and vice versa. Among the cations, copper has catalytic effects on the oxidation process. A higher buffer value of water has also a positive effect. 

The buffer value of water (BV) expresses the ability to resist, or buffer, pH changes after addition of acids and bases. It can be defined as a ratio of an infinitesimal addition of a strong base Cj, or strong acid in mol 1 to the corresponding pH change induced in the following way ... 

The buffer value of a solution can be evaluated from the course of the neutralization titration curve. It is a reciprocal value of the tangent to the titration curve expressing the dependence pH = for the given points. The buffer value is given in mmol 1 and is always positive. 

A number of homogeneous and heterogeneous buffer systems can be found in water. The most important buffer system in natural waters is CO2-HCO3-CO3 . Maximum buffer values in this system are achieved at equal concentrations of hydrogen carbonates and carbonates which are at pH of about 6.3 when c(H ) = and at pH of about 10.3 when c(H ) = K2- The carbonate system has the minimum capacity at pH 8.3,... 

In wastewaters the NHg-NH buffer system needs to be considered. The total buffer value is given by the sum of partial buffer values for natural water this ranges from tens to units of mmol 1 . ... 

During the anaerobic stabilization of sludges from wastewater treatment plants, the buffer value of undissolved carbonates is particularly important. 

Acid or base capacities are therefore measured in mmol 1 . The pH value up to which the titration takes place, is presented as the index of the relevant abbreviation, e.g. ANC4 3, ANC5 75, BNC7 q, etc. The neutralizing capacity is an integral of the buffer value within given pH range. 

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