Sodium acetate constants

In a 250 ml. flask place 75 ml, of water, 24 g. (20 ml.) of concentrated hydrochloric acid and 14g. (13-7 ml.) of aniline. Shake vigorously (1) and then add 50 g. of crushed ice. Rim in a solution of 5-2 g. of so um nitrite in 12 ml. of water, with constant shaking, during a period of 5-10 minutes. Allow to stand with frequent shaking (1) for 15 minutes, and add a solution of 21 0 g. of crystallised sodium acetate in 40 ml. of water during 5 minutes. A yellow precipitate of diazoaminobenzene begins to form immediately allow to stand with frequent shaking for 45 minutes and do not allow the temperature to rise above 20° (add ice. 

Azlactone of a-benzoylaminocinnamic acid. Place a mi.xture of 27 g. (26 ml.) of redistilled benzaldehyde, 45 g. of Mppuric acid (Section IV,54), 77 g. (71-5) ml. of acetic anhydride and 20-5 g. of anhydrous sodium acetate in a 500 ml. conical flask and heat on an electric hot plate with constant shaking. As soon as the mixture has liquefied completely, transfer the flask to a water bath and heat for 2 hours. Then add 100 ml. of alcohol slowly to the contents of the flask, allow the mixture to stand overnight, filter the crystalline product with suction, wash with two 25 ml. portions of ice-cold alcohol and then wash with two 25 ml. portions of boiling water dry at 100°. The yield of almost pure azlactone, m.p. 165-166°, is 40 g. Recrystallisation from benzene raises the m.p. to 167-168°. 

If a solution of acetic acid at equilibrium is disturbed by adding sodium acetate, the [CHaCOO-] increases, suggesting an apparent increase in the value of K. Since Ka must remain constant, however, the concentration of all three species in equation 6.26 must change in a fashion that restores to its original value. In this case, equilibrium is reestablished by the partial reaction of CHaCOO and HaO+ to produce additional CHaCOOH. 

Suppose you need to prepare a buffer with a pH of 9.36. Using the Henderson-Hasselbalch equation, you calculate the amounts of acetic acid and sodium acetate needed and prepare the buffer. When you measure the pH, however, you find that it is 9.25. If you have been careful in your calculations and measurements, what can account for the difference between the obtained and expected pHs In this section, we will examine an important limitation to our use of equilibrium constants and learn how this limitation can be corrected. 

The ionization eonstant should be a function of the intrinsic heterolytic ability (e.g., intrinsic acidity if the solute is an acid HX) and the ionizing power of the solvents, whereas the dissoeiation constant should be primarily determined by the dissociating power of the solvent. Therefore, Ad is expeeted to be under the eontrol of e, the dieleetrie eonstant. As a consequenee, ion pairs are not deteetable in high-e solvents like water, which is why the terms ionization constant and dissociation constant are often used interchangeably. In low-e solvents, however, dissociation constants are very small and ion pairs (and higher aggregates) become important species. For example, in ethylene chloride (e = 10.23), the dissociation constants of substituted phenyltrimethylammonium perchlorate salts are of the order 10 . Overall dissociation constants, expressed as pArx = — log Arx, for some substanees in aeetie acid (e = 6.19) are perchloric acid, 4.87 sulfuric acid, 7.24 sodium acetate, 6.68 sodium perchlorate, 5.48. Aeid-base equilibria in aeetie acid have been earefully studied beeause of the analytical importance of this solvent in titrimetry. 

Example 11. Calculate (i) the hydrolysis constant, (ii) the degree of hydrolysis, and (iii) the hydrogen ion concentration of a solution of sodium acetate (0.01 mol L-1) at the laboratory temperature. 

Weak acid with a strong base. In the titration of a weak acid with a strong base, the shape of the curve will depend upon the concentration and the dissociation constant Ka of the acid. Thus in the neutralisation of acetic acid (Ka— 1.8 x 10-5) with sodium hydroxide solution, the salt (sodium acetate) which is formed during the first part of the titration tends to repress the ionisation of the acetic acid still present so that its conductance decreases. The rising salt concentration will, however, tend to produce an increase in conductance. In consequence of these opposing influences the titration curves may have minima, the position of which will depend upon the concentration and upon the strength of the weak acid. As the titration proceeds, a somewhat indefinite break will occur at the end point, and the graph will become linear after all the acid has been neutralised. Some curves for acetic acid-sodium hydroxide titrations are shown in Fig. 13.2(h) clearly it is not possible to fix an accurate end point. 

The pH 5.5 method To an activated sample (<10 xl), 3 ml of 10 mM sodium acetate buffer (pH 5.5), 5-10 mg of CTAB, 20 xl of 0.1 M FeS04, and 20 xl of 10% H2O2 are added in that order. The light emission is triggered when H2O2 is injected with a constant rate syringe (Hamilton CR-700-20). 

Solid-surface room-temperature phosphorescence (RTF) is a relatively new technique which has been used for organic trace analysis in several fields. However, the fundamental interactions needed for RTF are only partly understood. To clarify some of the interactions required for strong RTF, organic compounds adsorbed on several surfaces are being studied. Fluorescence quantum yield values, phosphorescence quantum yield values, and phosphorescence lifetime values were obtained for model compounds adsorbed on sodiiun acetate-sodium chloride mixtures and on a-cyclodextrin-sodium chloride mixtures. With the data obtained, the triplet formation efficiency and some of the rate constants related to the luminescence processes were calculated. This information clarified several of the interactions responsible for RTF from organic compounds adsorbed on sodium acetate-sodium chloride and a-cyclodextrin-sodium chloride mixtures. Work with silica gel chromatoplates has involved studying the effects of moisture, gases, and various solvents on the fluorescence and phosphorescence intensities. The net result of the study has been to improve the experimental conditions for enhanced sensitivity and selectivity in solid-surface luminescence analysis. 

Solid-surface fluorescence and phosphorescence quantum yield values were obtained from +23° to -180°C for the anion of p-aminobenzoic acid adsorbed on sodium acetate (11). Fhosphorescence lifetime values were also obtained for the adsorbed anion from +23° to -196°C. Table 1 gives the fluorescence and phosphorescence quantum yield values acquired. The fluorescence quantum yield values remained practically constant as a function of temperature. However, the phosphorescence quantum yield values changed substantially with temperature. The phosphorescence lifetime experiments indicated two decaying components. Each component showed a gradual increase in phosphorescence lifetime with cooler temperatures, but then the increase appeared to level off at the coldest temperatures. 

Several fundamental luminescence parameters were calculated for the anion of p-aminobenzoic acid on sodium acetate (11). The triplet formation efficiency (( ), the rate constant for phosphorescence... 

Sodium Acetate-Sodium Chloride Mixtures. Ramasamy and Hurtubise (12) obtained RTF and RTF quantum yields, triplet formation efficiency, and phosphorescence lifetime values for the anion of p-aminobenzoic acid adsorbed on sodium acetate and on several sodium acetate-sodium chloride mixtures. Rate constants were calculated for phosphorescence and for radiationless transition from the triplet state. The results showed that several factors were important for maximum RTF from the anion of p-aminobenzoic acid. One of the most important of these was how efficiently the matrix was packed with sodium acetate molecules. A similar conclusion was found for RTF however, the RTF quantum yield increased more dramatically than the RTF quantum yield. 

Solvolysis of either 178a or 178b in 80% aqueous ethanol in the presence of p-toluenethiolate or benzylthiolate gives a 1 1 mixture of cis and trans products. A 1 1 ds trans product ratio also was observed in acetic acid in the presence of either sodium acetate or silver acetate. The 1 1 product ratio was observed as early as 10% reaction and remained constant throughout the reaction. The acetolysis is accompanied by extensive ion-pair return, which causes cis trans, 178a 178b, isomerization. However, this isomerization... 

The pectin/sucrose gels were characterized as follows (amounts per lOOg gel) 0.3 g AUA, 65% soluble solid substance, 0.01 mol sodium acetate / lactic acid buffer, pH 3.0 (20°C). The metal ions were added as combinations of chlorides according to a mixture design with constant amount of chloride ions (2.5 mmol / lOOg gel). Thus the total amount of metal ions... 

Verhoef and co-workers suggested omitting the foul smelling pyridine completely and proposed a modified reagent, consisting of a methanolic solution of sulphur dioxide (0.5 M) and sodium acetate (1M) as the solvent for the analyte, and a solution of iodine (0.1 M) in methanol as the titrant the titration proceeds much faster and the end-point can be detected preferably bipoten-tiometrically (constant current of 2 pA), but also biamperometrically (AE about 100 mV) and even visually as only a little of the yellow sulphur dioxide-iodide complex S02r is formed (for the coulometric method see Section 3.5). 

Sodium Acetate Complexes of U(VI), Np(VI), Pu(VI) and Am(VI). A Comparison of Metal Oxygen Bond Distance and Bond Force Constant in this Series. Report AECU-3088 (1954). J- chem. Phys. 23, 2105 (1955). 

Fig. 9. The 3/Hn coupling constants versus temperature for different alanine residues in XAO peptide. The reversibility of 3/hn coupling constant versus temperature was checked by measurements with temperature increasing from 2° to 56°C (labeled as heating) or decreasing from 56° to 6°C (labeled as cooling). The errors are the same in heating and cooling measurements the error bars are shown only for heating measurements for clarity. The conditions were temperature from 2° to 56°C, concentration ca. 4 mM, in 30 mM sodium acetate buffer (pH = 4.6, 10% D20 ). From Shi et al. (2002). Proc. Natl. Acad. Sd. USA 99, 9190-9195, 2002 National Academy of Sciences, USA.

This reaction is found to be stable in sodium acetate and acetic acid buffer (pH 4.65), and so it has only been studied in this medium. The faradaic rectification theory becomes highly complicated when extended to three-electron charge transfer reactions due to the formation of the two intermediate species Al(II) and A1(I). In order to determine the three rate constants and the two unknown concentration terms, C°Rl and C°Ru, corresponding to the two intermediate species formed, it becomes necessary to carry out the experiment at five different concentrations of aluminum ion, each below 2.00 mM. 

Acetyl chloride (54 g. =075 mole) is allowed to run drop by drop from a tap funnel on to 80 g. of finely powdered anhydrous sodium acetate prepared in the manner described below. When about half of the chloride has been added the experiment is interrupted for a short time in order to stir the pasty mass of material with a bent glass rod, the lower end of which has been flattened. The rest of the acetyl chloride is then run in at such a rate that none passes over unchanged. The anhydride is now distilled from the residual salt by mean of a luminous flame kept constantly in motion. Complete conversion of the last traces of unchanged acetyl chloride to acetic anhydride is attained by adding 3 g. of finely powdered anhydrous sodium acetate to the distillate, which is finally fractionally distilled. Boiling point of acetic anhydride 138°. Yield 55-60 g. Use for acetylation, in Perkin s synthesis (Chap. V. 8, p. 232), preparation of acetophenone (Chap. IX. 3 6, p. 346). 

Mechanistic aspects of the intermolecular cyclization reaction in the anodic oxidation of catechol in the presence of 4-hydroxycoumarin were discussed in Sect. 2.2. This reaction is a synthetically simple and versatile method for the preparation of formally [3 + 2] cycloadducts between a -diketo compound and catechol [44,45]. Anodic oxidation of catechol using controlled potential electrolysis (E = 0.9-1.1 V vs SCE) or constant current electrolysis (i = 5 mA/cm ) was performed in water solution containing sodium acetate (0.15 mol/1) in the presence of various nucleophiles such as 4-hydroxycoumarin,... 

In a high-pressure liquid chromatography assay of aspirin tablets, 10 extracts are made and the extracts are diluted with mobile phase solution, which consists of acetonitrile/0.1 M sodium acetate buffer pH 4.5 (10 90) and analysed sequentially. If the rate constant for the degradation of aspirin in the mobile phase is O.OfOl h " at room temperature how long can the andyst store the solutions at room temperature before the degradation of the analyte is greater than 0.5% ... 

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