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Acidity measurement procedure

Descriptions of sulfuric acid analytical procedures not specified by ASTM are available (32,152). Federal specifications also describe the requited method of analysis. Concentrations of 78 wt % and 93 wt % H2SO4 are commonly measured indirectly by determining specific gravity. Higher acid concentrations are normally determined by titration with a base, or by sonic velocity or other physical property for plant control. Sonic velocity has been found to be quite accurate for strength analysis of both filming and nonfuming acid. [Pg.192]

The most common methods used to determine protein concentration are the dye-binding procedure using Coomassie brilliant blue, and the bicinchonic-acid-based procedure. Various dyes are known to bind quantitatively to proteins, resulting in an alteration of the characteristic absorption spectrum of the dye. Coomassie brilliant blue G-250, for example, becomes protonated when dissolved in phosphoric acid, and has an absorbance maximum at 450 nm. Binding of the dye to a protein (via ionic interactions) results in a shift in the dye s absorbance spectrum, with a new major peak (at 595 nm) being observed. Quantification of proteins in this case can thus be undertaken by measuring absorbance at 595 nm. The method is sensitive, easy and rapid to undertake. Also, it exhibits little quantitative variation between different proteins. [Pg.180]

Inherent in all these methodologies, which measure either absolute Sr levels or strontium isotope ratios in mineralized tissue, is the assumption that diagenesis has not altered the signal since death. This has been a matter of some considerable debate (e.g., Nelson et al. 1986), but the consensus of current opinion amongst practitioners is that the repeated acid-washing procedures used remove any diagenetic mineral, because it has a higher... [Pg.190]

Infrared Procedures. Acidity Measurements. Zeolites treated as for catalytic experiments (heating in a stream of dry air and equilibration with H20 vapor at room temperature) were compressed at 1000 kg/cm2. The resulting disks (5 mg/cm2) were mounted in a quartz sample holder which was introduced into an IR cell as previously described (18). They were heated slowly under vacuum (the temperature was raised stepwise up to 450° in 5 hours). At 450°C, 02 was admitted, and the cell, connected to a liquid nitrogen trap, was maintained at this temperature for 4-5 hours. Finally the wafers were evacuated overnight at 450° C. The vapor of thoroughly dried pyridine was allowed to equilibrate with the wafer at room temperature. Afterwards, the pyridine was desorbed at a series of increasing temperatures for 15 hours each time. [Pg.468]

All biochemical laboratory activities, whether in education, research, or industry, are replete with techniques that must be carried out almost on a daily basis. This chapter outlines the theoretical and practical aspects of some of these general and routine procedures, including use of buffers, pH and other electrodes, dialysis, membrane filtration, lyophilization, centrifugal concentration, and quantitative methods for protein and nucleic acid measurement. [Pg.36]

For a selected list of elements (26) there is another acid treatment procedure which is readily applicable to the analysis of orange juice this procedure involves hydrolysis with moderately strong nitric acid to breakdown most of the sugars and to decrease the size of the pulpy constituents. The solution is then filtered, diluted, and measured by atomic absorption. For elements that can be determined with an air-acetylene flame using a high solids (three slot) burner, this procedure offers a useful alternative. Fricke et al. (33) also mentions the utility of this method and gives comparative results on the use of this method in sample preparation. [Pg.371]

A reliable method of measuring the mineral matter content of a coal is an acid demineralization procedure. The method depends on the loss of weight of a sample when treated with 40% hydrofluoric acid at 50 to 60°C (122 to 140°F). Treatment of the sample with hydrochloric acid before and after treatment with hydrofluoric acid helps prevent the retention of insoluble calcium fluoride (CaF2) in the coal. Pyrite is not dissolved in the treatment, consequently, pyrite and a small amount of retained chloride must be determined separately. Since two-thirds of the mass of the pyrite (FeS2) is accounted for by the presence of ferric oxide (Fe203) in the residual ash, the mineral matter content is then given by the formula... [Pg.99]

Samples USY-1, USY-2 and U1F-25, U2F-15, U2F-35 were obtained following the procedure described in the previous paper (14). Moreover, a new USY sample (U1F-25S) was obtained by steaming sample U1F-25 at 750 C and 100% steam during 5 hours. Acidity measurements were carried out on wafers of 10 mg.cm"2 previously degassed in a I.R. cell at 400°C and 10"3 Pa, overnight. 6.66.102 Pa of pyridine were introduced into the cell at room temperature. After equilibrium, the samples were... [Pg.18]

The protocol can be adapted to measure receptor recycling. If radiolabeled antibodies are internalized into cells by incubation at 37°C in the presence of chemokine or other agents, the acid-elution procedure can be used to remove radiolabeled antibodies remaining on the cell surface. If the acid-elution medium is not reduced below pH 3.0, and the washes kept brief and performed at 4°C, then the cells can be returned to 37°C culture (care should be taken to ensure that the endocytic-trafficking properties of cells are not perturbed by the low pH treatment). During a subsequent incubation at 37°C, receptors that recycle will return antibodies to the cell surface. These antibody molecules can be assessed by measuring the radioactivity that becomes accessible to a second round of acid elution. [Pg.206]

It should be noted at this point that there is a consistency in the pKa values measured in pure DMSO by the various techniques. However, there is some uncertainty at present relating to pKa values obtained by acidity function procedures in alcoholic and aqueous DMSO media. Thus one has the unexpected situation that theoretical analysis of the medium effect on p/ a is hampered because the values for a number of weak acids referring to the standard state in water are in doubt. Under these circumstances less than critical application of (6) to many weak acids, including some carboxylic acids, phenols as well as carbon acids, is inadvisable. Of course, (6) is strictly applicable to those cases in which the p/sfa values can be measured in the pure hydroxylic solvents and also for those weak acids which obey the criteria outlined by Cox and Stewart (1976). Despite this difficulty there is now a large body of reliable pKa data in both DMSO and water. Thus in principle it should be possible to account for variations, or reversals, in acidity order in terms of the thermodynamic transfer functions in (6). [Pg.149]

Determination of Octanol/Water Partition Coefficients. Since oc-tanol/water partition coefficient data for trifluoromethanesulfonanilide (I) and its substituted derivatives have not been reported in the literature and since it was not apparent that any of the substituent tt values previously determined by Fujita et al. (11) would be directly applicable to the TFMS herbicidal system, all TFMS partition coefficients and tt values were determined experimentally. The fluoroalkanesulfonanilides are very acidic because of the electron-withdrawing power of the parent fluoro-alkanesulfonyl group (5). The parent TFMS compound (I), for example, has a pKa in water of 4.45 at 25 °C. This inherent acidity extends to all TFMS series members and requires that the usual partition coefficient measurement procedure described by Fujita et al. (11) be modified to obtain accurate values of log P and tt. [Pg.195]

The 2-(3,5-dimethoxyphenyl)prop-2-yloxycarbonyl group (Ddz) (Scheme 38) was developed by Birr et al. as an alternative to the Bpoc group which for most synthetic purposes is too acid labile, since A -Bpoc-protected amino acids are occasionally cleaved by their intrinsic acidity.b l Kinetic measurements revealed that the relative cleavage rates of Boc, Ddz, and Bpoc are 1 1400 3000 (for various acid deprotection procedures, see Table 10).b l... [Pg.105]

The pentosan content is measured by converting the pentosan to furfural, and by then determining the furfural, usually by precipitation with barbituric acid. The procedure is described... [Pg.34]

ZSM-5 zeolites modified by conventional and solid-state ion-exchange were characterized by X-ray diffraction, BET measurements, derivatography, IR spectroscopy in the framework vibration range and acidity measurements with pyridine as probe. NO adsorption and transformation on Cu-, Co-, Ni- and FeZSM-5 zeolites were followed by IR spectroscopy. Mono- and dinitrosyl surface species, adsorbed NjO and NO were detected in different concentrations on the tested catalysts. Differences in adsorption behaviour were observed for samples exchanged by the conventional and solid-state procedures. [Pg.665]

The dry-ashing plus acid digestion of tea leaves (Section 1.1) and the available phosphorus extraction (Section 1.3) are contrasting procedures in regard to the acceptable precision of the determination. In one the sample is weighed to 0.1 mg ( 0.02%), whereas in the other the 5 cm3 scoop used for measuring soil, may introduce a variation of 0.2 g ( 4%). You may like to think about this. Is the sample measuring procedure appropriate for the purpose of the analysis in each case ... [Pg.76]

In titrimetric methods, LPS catalyzes the hydrolysis of fatty acids from an emulsion of olive oil or oleic acid. The fatty acids liberated are titrated with dilute allcali. Kinetic versions use an automated potentiometric titrator (an instrument commonly referred to as a "pH-stat ). The amount of aUcah used is recorded as a function of time and serves as a measure of fatty acid produced during the reaction. This method has been proposed as reference measurement procedure, useful in the evaluation of new LPS methods. ... [Pg.621]

The diagnosis of D-lactic acidosis is suspected in patients with disorders of the small intestine causing malabsorption and when the serum anion gap (Chapter 39) is elevated in the presence of normal serum levels of L-lactate and other organic acids. Measurement of serum D-lactate requires special enzymatic procedures utilizing D-lactate dehydrogenase and NADH. As D-lactate is converted to pyruvate, NADH is oxidized to NAD+ which is detected spectrophotometrically (Chapter 8). [Pg.236]

Aqueous Solutions. Two measurement procedures for aqueous solutions were evaluated in the Project—atomic absorption (AA) with an air-acetylene flame and heated vaporization atomic absorption. Optimum parameters for both measurements were established empirically from the response for standard solutions of cobalt in dilute hydrochloric acid. [Pg.111]


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See also in sourсe #XX -- [ Pg.296 ]




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