Buffers properties

C18-0043. Which of the following solutions show buffer properties Compute the pH of each solution that is buffered. 

Buffering properties are exhibited by mixtures of weak acids (or bases) and their salts with a composition such that the concentration of the weak component and the salt are not too far apart. Thus, for b = sy pH = pK A(HA). The addition of a quite large amount of strong hydroxide or acid to such a mixture results in a small pH change in the solution (see Fig. 1.9). 

At greater depths, the redox characteristics are mainly determined by another mineral system fayalite (Fe2Si04), magnetite and quartz (Si02) (theFMQ system). The buffer properties of the two systems can be expressed in terms of the following equations ... 

Bacterial cell walls contain different types of negatively charged (proton-active) functional groups, such as carboxyl, hydroxyl and phosphoryl that can adsorb metal cations, and retain them by mineral nucleation. Reversed titration studies on live, inactive Shewanella putrefaciens indicate that the pH-buffering properties of these bacteria arise from the equilibrium ionization of three discrete populations of carboxyl (pKa = 5.16 0.04), phosphoryl (oKa = 7.22 0.15), and amine (/ Ka = 10.04 0.67) groups (Haas et al. 2001). These functional groups control the sorption and binding of toxic metals on bacterial cell surfaces. 

The volume of solution in the subsurface, under partially saturated conditions, varies with the physical properties of the medium. In the soil layer, the composition of the aqueous solution fluctuates as a result of evapotranspiration or addition by rain or irrigation water to the system. Changes in the solution concentration and composition, as well as the rate of change, are controlled by the buffer properties of the sohd phase. Because of the diversity in the physicochemical properties of the sohd phase, as well as changes in the amount of water in the subsurface as result of natural and human influences, it is difficult to make generalizations concerning the chemical composition of the subsurface aqueous solution. 

Some commonly used buffers, such as sodium and potassium phosphate, are incompatible with ELSD, but there are ready alternatives. For example, ammonium acetate has similar buffering properties to potassium phosphate, and ammonium carbonate, ammonium formate, pyridinium acetate, and pyridinium formate are options for different pH ranges. Typical mobile phase modifiers that do not meet the volatility criteria can be replaced by a wide variety of more volatile alternates. For example, phosphoric acid, commonly used as an acid modifier fo control pH and ionization, can be replaced by trifluoroacetic acid other acids that are sufficiently volatile for use with FLSD include, acetic, carbonic, and formic acids. Triethylamine, commonly used as a base modifier, is compatible with FLSD other base modifiers that can be used are ethylamine, methylamine, and ammonium hydroxide [78]. 

In theory, it should be possible to calculate the overall buffering properties of milk by combining the titration curves for all components but in... 

The second novelty of our work is the elucidation of the role of pH-buffers in swelling equilibria and kinetics. It is interesting to note that most physical chemists choose not to use buffers because they complicate the system under study. On the other hand, any ultimate biological application of gels is likely to involve some sort of buffered medium. As we have shown, buffer properties such... 

Calcium and phosphorus influence curd buffering properties and ripening characteristics. The calcium content in cheese may be determined by... 

Borax decahydrate (also called borax) is slightly soluble in cold water (4.71% by wt. at 20°C) and highly soluble in hot water (30% at 60°C). It has a pH of 9.24 (1% solution at ambient temperature) and exhibits excellent buffering property.7 As a crystalline material, borax decahydrate is stable under normal storage conditions. It will slowly lose water of crystallization if exposed to a warm and dry atmosphere. Conversely, exposure to a humid atmosphere can cause recrystallization at particle contact point, thus resulting in caking. 

Borax pentahydrate (also known as Neobor ) is the most common form of sodium borate used in a variety of industries. Its advantages when compared with borax lie in the lower transportation, handling, and the storage cost of a more concentrated product. Borax pentahydrate readily effloresces upon heating. It starts to dehydrate at about 65°C, loses all water of hydration when heated above 320°C, and fuses when heated above 740°C. In water, it hydrolyzes to give a mildly alkaline solution with excellent buffering properties.7... 

Combining thermal- with pH-dependent gelation, Kumar et al. [86] developed a combination of methylcellulose 15% and carbopol 0.3%. This composition exhibited a sol-to-gel transition between 25 and 37 °C with a pH increase from 4 to 7.4 [203], A possible mechanism for the thermal effect could be the decrease in the degree of the methylcellulose hydration, while the polyacrylic acid can transform into a gel upon an increase in pH due to the buffering properties of the tear fluid [1]. 

Thank you, Professor Lag. I have another question. You have mentioned a very important factor, that influences very much also the effect of acid deposition. The poor buffering properties of your soil. Which are mainly, granitic. 

The bioavailability of acetylsalicylic acid from three different dosage forms—two types of effervescent tablets with different buffering properties and tablets of a conventional type— was studied in healthy volunteers. Complete absorption was found for all the preparations studied. Both effervescent tablets were rapidly absorbed. The buffering properties did not influence the rate of absorption.f ... 

Brown and Kaplan made use of the buffering property of oils in phenol solutions. Their formulation contained up to 95% phenol combined with oils. A patch test behind the ear had to be carried out before the facial peel. If there was skin necrosis, they reduced the strength of the phenol by gradually adding oil in small quantities until the right dose was found for the patient s skin. To increase the strength of the mixture, on the other hand, soap (saponified cresol) was added or the concentration of phenol was increased. 

The first deep basin downstream of the entrance sills is the Bornholm Basin (Fig. 10.1). This basin has a maximum depth of more than 90 m and is separated from the next downstream basin by the Slupsk Sill (sill depth 60 m). The buffering properties of the Bornholm Basin play an essential part for the effectiveness of MBls in other central basins. The thermohaline conditions in the Bornholm Basin are also considerably important for the evolution of stagnation in the central Baltic deepwater. In general, there is a frequent inflow of lower amounts of highly saline water that penetrates across the sills into the ArkonaBasin during each baroclinic or weak barotropic inflow event. This water is trapped into the... 

Mass transfer enhancement depends on the buffering properties and diffusivity of the additive. Cavanaugh (14) measured effective pka values of buffer alternatives at scrubber conditions. Chang and Rochelle (16) developed a model of enhancement based on mass transfer with equilibrium reactions and experimentally demonstrated its effectiveness with acetic and adipic acid at 25°C. In this paper, we present experimental and model results at 55°C with several buffer alternatives (17). 

Adipic acid has attractive buffer properties and it is cost-effective, non toxic, and commercially available in large quantities. It coprecipitates with CaS03 and is subject to oxidative degradation, but these problems should be minimized by using forced oxidation at low pH with high concentrations of dissolved Mn. 

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