Total acidity determination

Total acidity determined by the barium hydroxide method (14). 

Thus, questions remain the large differences in acidity reported here might be attributed both to the nature of the catalysts (affected by the method of preparation, the loadings of the different elements, and whether the catalysts are in the oxide or sulfided states) and to the method of acidity measurement (total acidity determination or selective titration of acid sites with a specific strength). Furthermore, the protocols for measurement (e.g., the temperature and duration of outgassing before acidity determination) may also affect the results. Therefore, it can be inferred that some standardization of measurement conditions is required to reach consensus regarding the influence of phosphorus on the acidity of hydrotreating catalysts. 

X 10 M, when the quinone concentration is at 3 x 10 M. Based on this, the total acid determination can be made by measuring the prepeak height. 

The half-peak potential of the prepeak shifted to a negative value along with an increase in pK of the added acid. In the presence of mixed acids in the solution, stepwise prepeaks may appear when their pK values are different enough from each other. On the other hand, when the acid strengths and diffusion coefficients were nearly the same for all the acids, only one prepeak could be observed at an identical potential with a height proportional to the sum of the total acid concentration for all the acids. In such cases, the total acid determination can be made by measuring the prepeak height. 

This chapter dealt with the FIA-ECD method applied to total acid determination in foods, beverages, and pH control agents. Acid content in food is one of the most important... 

In the end, our method for total acid determination was established based on the qui-none-mediated amperometric signaling for the total amount of acid species. The method was thus shown to have potential in a broad range of applications for checking the quality of food materials. 

CO2 is determined by titrating with a standard solution of NaOH to the phenolphthalein end point, or to a pH of 8.3, with results reported as milligrams CO2 per liter. This analysis is essentially the same as that for the determination of total acidity, and can only be applied to water samples that do not contain any strong acid acidity. 

Acidity is determined by glc or titration, and the dimer content of acryhc acid by glc or a saponification procedure. The total acidity is corrected for the dimer acid content to give the value for acryhc acid. 

Analytical Procedures. Standard methods for analysis of food-grade adipic acid are described ia the Food Chemicals Codex (see Refs, ia Table 8). Classical methods are used for assay (titration), trace metals (As, heavy metals as Pb), and total ash. Water is determined by Kad-Fisher titration of a methanol solution of the acid. Determination of color ia methanol solution (APHA, Hazen equivalent, max. 10), as well as iron and other metals, are also described elsewhere (175). Other analyses frequendy are required for resia-grade acid. For example, hydrolyzable nitrogen (NH, amides, nitriles, etc) is determined by distillation of ammonia from an alkaline solution. Reducible nitrogen (nitrates and nitroorganics) may then be determined by adding DeVarda s alloy and continuing the distillation. Hydrocarbon oil contaminants may be determined by ir analysis of halocarbon extracts of alkaline solutions of the acid. 

The most common chromatogram in the distilled spirits industry is the fusel oil content. This consists of / -propyl alcohol, isobutyl alcohol, and isoamyl alcohol. Other common peaks are ethyl acetate, acetaldehyde, and methanol. The gc columns may be steel, copper, or glass packed column or capillary columns. Additional analyses include deterrninations of esters, total acids, fixed acids, volatile acids, soHds or extracts (used to determine... 

Total acidity and total chlorides can be deterrnined by conventional techniques after hydrolysing a sample. Satisfactory procedures for determining hydrogen chloride and free-sulfiir trioxide are described in the Hterature (18,41). Small amounts of both hydrogen chloride and sulfur trioxide can be found in the same sample because of the equiUbrium nature of the Hquid. Procedures for the direct deterrnination of pyrosulfuryl chloride have also been described (42,43), but are not generally required for routine analysis. Small concentrations of sulfuric acid can be deterrnined by electrical conductivity. 

Naphthenic acid is a collective name for organic acids present in some but not all crude oils. In addition to true naphthenic acids (naphthenic carboxylic acids represented by the formula X-COOH in which X is a cycloparaffin radical), the total acidity of a crude may include various amounts of other organic acids and sometimes mineral acids. Thus the total neutralization number of a stock, which is a measure of its total acidity, includes (but does not necessaiily represent) the level of naphthenic acids present. The neutralization number is the number of milligrams of potassium hydroxide required to neutralize one gram of stock as determined by titration using phenolphthalein as an indicator, or as determined by potentiometric titration. It may be as high as 10 mg KOH/gr. for some crudes. The neutralization number does not usually become important as a corrosion factor, however, unless it is at least 0.5 mg KOH/gm. 

In the wine industry, FTIR has become a useful technique for rapid analysis of industrial-grade glycerol adulteration, polymeric mannose, organic acids, and varietal authenticity. Urbano Cuadrado et al. (2005) studied the applicability of spectroscopic techniques in the near- and mid-infrared frequencies to determine multiple wine parameters alcoholic degree, volumic mass, total acidity, total polyphenol index, glycerol, and total sulfur dioxide in a much more efficient approach than standard and reference methods in terms of time, reagent, and operation errors. 

Figure 2. Analysis of free (A) and total (B) acids in wild type (open bars) and transgenic (closed bars) plants. Fig. 2C shows the ratio of free to total acids (in %). The bars represent the mean +/- S.E. of 4-11 independent determinations.

Portions (50 mU MCA-hydrolsing activity) of purified CinnAE were incubated at 37°C with SBP (10 mg), both in the presence and absence of other carbohydrases, in 100 mM MOPS (pH 6.0) in a final volume of 1 mL. Incubations containing boiled enzyme were performed as controls. Reactions were terminated by boiling (3 min) and the amount of free ferulic acid determined using a method described previously for de-starched wheat bran [18]. The total amount of alkali-extractable ferulic acid present in the SBP was 0.87% [5]. 

The purified sulfuric acid (i.e., preheated the commercial ultrapure grade H2SO4 at 200°C for 24 hr under vacuo to remove its decarboxylating contaminants and subsequently cooled to ambient temperature), 0.5 ml, was added to the bottom well of the decarboxylation flask and subsequently placed under vacuo. A known amount of a GC-standard (640 mm of 100 ppm C2Hg in He) was introduced into the flask for the total CO2 determination. The acid was then allowed to dissolve the photodegraded residual film on the side of the flask by tilting. The acid solution was left standing for 20 minutes at room temperature. 

Florin THJ. 1991. Hydrogen sulphide and total acid-volatile sulphide in feces, determined with a direct spectrophotometric method. Clin Chim Acta 196 127-134. 

Chemical composition was determined by elemental analysis, by means of a Varian Liberty 200 ICP spectrometer. X-ray powder diffraction (XRD) patterns were collected on a Philips PW 1820 powder diffractometer, using the Ni-filtered C Ka radiation (A, = 1.5406 A). BET surface area and pore size distribution were determined from N2 adsorption isotherms at 77 K (Thermofinnigan Sorptomatic 1990 apparatus, sample out gassing at 573 K for 24 h). Surface acidity was analysed by microcalorimetry at 353 K, using NH3 as probe molecule. Calorimetric runs were performed in a Tian-Calvet heat flow calorimeter (Setaram). Main physico-chemical properties and the total acidity of the catalysts are reported in Table 1. 

The analytical phase generally involves the use of very dilute solutions and a relatively high ratio of oxidant to substrate. Solutions of a concentration of 0.01 M to 0.001 M (in periodate ion) should be employed in an excess of two to three hundred percent (of oxidant) over the expected consumption, in order to elicit a valid value for the selective oxidation. This value can best be determined by timed measurements of the oxidant consumption, followed by the construction of a rate curve as previously described. If extensive overoxidation occurs, measures should be taken to minimize it, in order that the break in the curve may be recognized, and, thence, the true consumption of oxidant. After the reaction has, as far as possible, been brought under control, the analytical determination of certain simple reaction-products (such as total acid, formaldehyde, carbon dioxide, and ammonia) often aids in revealing what the reacting structures actually were. When possible, these values should be determined at timed intervals and be plotted as a rate curve. A very useful tool in this type of investigation, particularly when applied to carbohydrates, has been the polarimeter. With such preliminary information at hand, a structure can often be proposed, or the best conditions for a synthetic operation can be outlined. 

Andreae [564] coprecipitated tellurium (V) and tellurium (VI) from seawater and other natural waters with magnesium hydroxide. After dissolution of the precipitate with hydrochloric acid, the tellurium (IV) was reduced to tellurium hydride in 3 M hydrochloric acid. The hydride was trapped inside the graphite tube of a graphite furnace atomic absorption spectrometer, heated to 300 °C, and tellurium (IV) determined. Tellurium (VI) was reduced to tellurium (IV) by boiling with hydrochloric acid and total tellurium determined. Tellurium (VI) was then calculated. The limit of detection was 0.5 pmol per litre and precision 10-20%. 

A feature of this analytical scheme is the marked reliance on infrared spectrometry and titrimetry. The former is particularly applicable to the qualitative characterization of unknown organic materials whilst titrimetry provides a rapid, precise and cheap means of quantitative analysis. The routine titrimetric determination of water, total acid (acid number) and total base (base number) forms a significant proportion of the work load in some analytical laboratories. It is instructive to consider how other techniques might have been applied to the solution of this particular problem, e.g. NMR spectrometry and chromatography. 

Hydrogen-iodine reaction, 13 770 Hydrogen-ion activity, 14 23-34 nonaqueous solvents, 14 32 pH determination, 14 24-27 pH measurement systems, 14 27-31 Hydrogen ion concentration (total acidity), 14 23... 

The analysis of acid present before irradiation was determined to be 2 x 10 6 mmol for a one micrometer films on a 2 inch wafer. This is a significant fraction of total acid present after irradiation. For a 0.5 mJ/cm2 dose, this is nearly 30% of the total acid content. However, the acid present before exposure is not significant for t-BOC thermolysis. No carbonyl infrared absorbance change was noted following softbake. 

The pH of a 50.00-mL sample of 0.06000 M strontium hydroxide is measured as it is titrated with a 0.1200 M hydrochloric acid. Determine the pH of the solution after the following total volumes of hydrochloric acid have been added. 

---