Acids measurement

When the acidities of hydrocarbons are discussed in terms of the relative stabilities of neutral and anionic forms, particularly with respect to the extent of electron delocalization in the anion, the appropriate data are equilibrium acidity measurements. We have just seen... 

The thermodynamic CH acidity of terminal acetylenes in the series of A-alkylpyrazoles was studied (83IZV466). These equilibrium CH acidity measurements were performed in DMSO by the method of remetallation (75ZOB1529). It reveals some regularities concerning the influence of the ring structure, the nature of other substituents, and the position of the ethynyl group on the acidity of ethynyl pyr azoles. 

For other acids measurements were not made over a wide range of temperature, but the value of the ratio Kp/Kd was determined at a single temperature—a temperature which in some cases lay above and in other cases below the temperature at which the value of K passed through its maximum value. Under these circumstances the situation needs to be looked into more carefully. 

Correction of pH level via caustic soda (after the degasser and before the BX) is standard practice. Because both acid regeneration and caustic pH correction are practiced, it is usual to isolate the plant from the mains by providing a break tank. The full plant therefore tends to be break tank, RW booster pump, acid measuring tank, WAC, degasser, degassed water booster pump, pH correction, and BX. A schematic layout of this type of plant is shown in Figure 9.3a. 

Aveston, J. (1965). The hydrolysis of the aluminium ion ultracentrifugal and acidity measurements. Journal of the Chemical Society, 4438-43. 

The a scale of hydrogen bond donor acidities measures the ability of a solvent to donate a proton in a solvent-solute hydrogen bond,... 

Starting as soon as the magnesium is in contact with the acid, measure the time required for the magnesium to react completely. Record the reaction time. 

Other Gas Reactions. Several other reactive gases or vapours were examined but found to be unsatisfactory. No ester formation ( 1745 cm"1) was found when oxidatized films were exposed to acetic acid or formic acid vapour. Alcohol/carboxylic acid reactions in the solid state have often been suggested as the source of ester products, but not substantiated (4,5). Gaseous ammonia reacted with carboxylic acid groups to give absorptions at 1550 cm"1 [-C(=0)-0 ] and 1300 cm"1 (NHi +). However, these absorptions were very broad and the method inferior to acid measurement by SF. Although N20 did not react with oxidized polyolefins, the reaction of N02 with oxi-... 

The specific surface area of the fresh and used catalysts was measured by nitrogen adsorption method (Sorptometer 1900, Carlo Erba Instruments). The catalysts were outgassed at 473 K prior to the measurements and the Dubinin equation was used to calculate the specific surface area. The acidity of investigated samples was measured by infrared spectroscopy (ATI Mattson FTIR) by using pyridine (>99.5%, a.r.) as a probe molecule for qualitative and quantitative determination of both Bronstcd and Lewis acid sites (further denoted as BAS and LAS). The amounts of BAS and LAS were calculated from the intensities of corresponding spectral bands by using the molar extinction coefficients reported by Emeis (23). Full details of the acidity measurements are provided elsewhere (22). 

Concerning the acidity measured by NH3 and pyridine adsorption calorimetry the obtained results are summarized in Table 2. 

Three zeolite crystallite sizes were used, namely 0.02, 1-1.5 and 10-15 pm range The first zeolite sample was obtained from PQ Corporation, the two other were kindly synthesized by the Laboratoire des Materiaux Mineraux , UMR 7016, Mulhouse, France. The three samples had the same framework Si/Al ratio (15) and the same Bronsted acidity (measured by infrared spectroscopy of adsorbed pyridine). They were used in their protonic form (HBEA). 

Amino acid measurements in ALH84001 are almost certainly the result of Antarctic ice contamination. Amino acids are readily soluble in water but PAHs are practically insoluble. Isotopic measurements of 14C show that terrestrial carbon is incorporated into the meteorite during extended stays in the Antarctic ice fields. In addition, microbial activity on the exposed surfaces provides an additional source of biogenic organic material that may be incorporated over time. 

The fatty acids measured by these techniques have all been small monomeric molecules. Lamar and Goerlitz [ 125] studied the acidic materials in highly coloured water and found that most of the nonvolatile material was composed of polymeric hydroxy carboxylic acids, with some aromatic and olefinic unsaturation. Their methods included gas, paper, and column chromatography with infrared spectrophotometry as the major technique used for the actual characterisation of the compounds. 

C.H. Lochmiiller and S.S. Saavedra, Conformational changes in a soil fulvic acid measured by time-dependent fluorescence depolarization, Anal. Chem., 58... 

Kluger and Lam, 1978. Comparison with the rate constant calculated for succinamic acid at 50° gives EM = 5 x 101. Correction for the better leaving group uses the ratio of rates for maleamic and maleanilic acids measured by Aldersley et al. (1974b) at 39°... 

The reference intermolecular reaction for the aliphatic compounds is the formation of ethyl acetate from ethanol and acetic acid measured under the same conditions (20% ethanol-water, ionic strength 0.4 M) by Storm and Koshland (1972a). The esterification of benzoic acid in methanol at 25° is 290 times slower than that of acetic acid (Kirby, 1972), so this factor is used to correct the EM s, calculated otherwise in the same way, for the hydroxybenzoic acids. For the phenolic acids see notes m and n b Rate constants are in units of dm3 mol-1 s-1 c Storm and Koshland, 1972a d Storm and Koshland, 1972b Bunnett and Hauser, 1965... 

Fig. 34. Vapor pressure of benzoic acid measured on a thermobalance with Knudsen effusion cell...

The first acidity measurement of aniline was reported by McEwen122. He assigned an ion-pair pK of 27 to aniline in benzene in relation to MeOH in benzene, which was assumed to have an ion-pair pKa of 16. Acidities of a number of substituted anilines were measured by means of the H method in H2O-DMSO mixture123, and by NMR124, calorimetric125 and electrochemical126 methods in liquid ammonia at —31 °C. 

Fig. 2.76. Chromatogram for a red wine sample using gradient elution and photodiode array detection. The peaks correspond to 1 = gallic acid, measured at 280 nm 2 = rutin, measured at 360 nm. Reprinted with permission from M. Lopez et al. [193].

Aveston J, Anacker EW, Johnson JS (1964) Hydrolysis of molybdenum (VI). Ultracentrifugation, acidity measurements, and Raman spectra of polymolybdates. Inorg Chem 3 735-746 Baes Jr. CF, Mesmer RE (1986) The Hydrolysis of Cations. Krieger Publishing Company, Melbourne, EL Barling J, Anbar AD (2004) Molybdenum isotope fractionation during adsorption by manganese oxides. Earth Planet Sci Lett, in press... 

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