Acid/base content

There are countless situations where the relative acidity or alkalinity of a substance or system is of critical importance. Agricultural conditions, water quality, food preservation, lung and kidney function—all are circumstances in which quantitative measures of acidity or basicity enable proper maintenance and regulation of vital processes. The term pH is widely used as an expression of acid/base content, but what is the origin of such nomenclature ... 

The effect of the presence of water in oil in terms of alkaline reserve of oil, pH (extract) and TBN value was investigated (Fox et al., 1990 Pawlak et al., 1985). The soluble acid/base content has been determined by extraction into either DI water, 7% synthetic sea water solution or aqueous ethanol mixture (1 1, v/v). Extraction of oil samples by aqueous ethanol mixture (1 1, v/v) was applied to new and used samples of an SAE 30 oil. The relationship between pH extracted in aqueous ethanol and TBN value is shown in curve I, Fig. 6.8. 

Solution chemistry to form a gel type of precursor type of solvent pH (acid/base content) water content precursor concentration temperature... 

The grafting of nucleic acid base derivatives with a hydroxyl group onto poly(ethyleneimine) polymer backbone was also carried out by the activated ester method. Since the reactivity of the lactone is low, the direct reaction of the lactone derivative with poly(ethyleneimine) was not effective. Therefore, the lactone derivatives were at first hydrolyzed to the 3-hydroxybutyric acid derivatives, followed by condensation with poly(ethyleneimine) using the activated ester method. The grafting reaction was carried out in N,N-dimethylformamide, where a small amount of 4-pyrrolidinopyridine was added as an effective catalyst. Nucleic acid base contents of the polymers were determined by UV spectroscope of hydrolyzed samples. A quantitative calculations were made by using the corresponding carboxyethyl derivatives as standards. The nucleic acid base units (unit mol%) on the polymer are tabulated in Table 1. 

As field conditions change, the chemical requirements can change. If the process is modified, for example, very low rates on electrostatic units, the chemical requirements can change. Seasonal changes bring paraffin-induced emulsion problems. Workovers contribute to solids and acid/base contents, which alters the emulsion stability. So no matter how satisfactory a demulsifier is at one point in time, it may not be satisfaetory over the life of the field. 

A double end point, acid—base titration can be used to determine both sodium hydrosulfide and sodium sulfide content. Standardized hydrochloric acid is the titrant thymolphthalein and bromophenol blue are the indicators. Other bases having ionization constants in the ranges of the indicators used interfere with the analysis. Sodium thiosulfate and sodium thiocarbonate interfere quantitatively with the accuracy of the results. Detailed procedures to analyze sodium sulfide, sodium hydro sulfide, and sodium tetrasulfide are available (1). 

One 1-ml aliquot is added to 1.0 ml of freshly-distilled 1,2-dibromo-ethane (bp 132°C) in an oven-dried flask which contains a static atmosphere of nitrogen or argon. After the resulting solution has been allowed to stand at 25°C for 5 min, it Is diluted with 10 rat of water and titrated for base content (residual base) to a phenolphthalein endpoint with standard 0.100 M hydrochloric acid. The second 1-mL aliquot is added cautiously to 10 ml of water and then titrated for base content (total base) to a phenol phthalein endpoint with standard aqueous 0.100 M hydrochloric acid. The methyllithium concentration is the difference between the total base and residual base concentrations.2 Alternatively, the methynithiura concentration may be determined by titration with a standard solution of sec-butyl alcohol employing 2,2 -bipyridyl as an indicator. 

Fiber Relative strength Specific gravity Normal moisture content (%) Maximum usable temperature ( F) Acid Base Organic solvent Other attribute... 

Only particular solvents are suitable for certain purposes. The choice depending, for instance, on their residual water content or their acid-base nature if Rf values are to be reproduced [1, 2]. Halogen-containing solvents may not be employed for the determination of chlorinated pesticides. Similar considerations apply to PAH analyses. Pro analyst grades are no longer adequate for these purposes. It is true that it would be possible to manufacture universally pure solvents that were adequate for all analytical purposes, but they would then be too expensive for the final user [3, 4]. 

One of the least expensive and popular techniques for the quant detn of bound N in energetic materials is that of titrimetry. There are currently three basic titrimetry systems used aq acid-base, redox and non-aqueous (involving both acid-base and redox systems in which there is association, not ionization of the re-actants). The simple aq acid-base titrimetry system has been shown, earlier in the article, being used in the Kjeldahl, De varda and Ter-Meulen procedures to detn liberated NH3. It is also utilized, for example, to detn nitrosyi-sulfuric acid in mixed acids, total acidity in nitric acid, NG in exp] oils, and the N content of... 

The content of a curriculum must be functional when dealing with societal activities necessary chemical concepts, skills and attitudes with respect to macro-micro thinking must be included. This can be derived from representative authentic tasks. The content of the curriculum should be considered as a chemical toolbox. The traditional content of the present chemistry curriculum, such as the stmcture of atoms, ionic theoiy, fundamental acid-base calculations, are not necessarily part of the chemical toolbox when addressing chemical and technological tasks. The validity of the toolbox (philosophical substmcture) is determined by the representative practices and tasks related to chemistry (cf need-to-know principle in context-based approaches). 

C18-0065. A laboratory technician wants to determine the aspirin content of a headache pill by acid-base... 

The Lux-Flood theory relates to oxide melts. Geologists have often used acid-base concepts for the empirical classification of igneous silicate rocks (Read, 1948). Silica is implicitly assumed to be responsible for acidity, and the silica content of a rock is used as a measure of its acid-base balance ... 

Hydrolysis of polyamide-based formulations with 6 N HC1 followed by TLC allows differentiation between a-aminocaproic acid (ACA) and hexamethylenedi-amine (HMD) (hydrolysis products of PA6 and PA6.6, respectively), even at low levels. The monomer composition (PA6/PA6.6 ratio) can be derived after chromatographic determination of the adipic acid (AA) content. Extraction of the hydrolysate with ether and derivatisa-tion allow the quantitative determination of fatty acids (from lubricants) by means of GC (Figure 3.27). Further HC1/HF treatment of the hydrolysis residue, which is composed of mineral fillers, CB and nonhydrolysable polymers (e.g. impact modifiers) permits determination of total IM and CB contents CB is measured quantitatively by means of TGA [157]. Acid hydrolysis of flame retarded polyamides allows to determine the adipic acid content (indicative of PA6.6) by means of HPLC, HCN content (indicative of melamine cyanurate) and fatty acid (indicative of a stearate) by means of GC [640]. Determination of ethylene oxide-based antistatic agents... 

Aqueous waste containing dissolved toxic organic material should be decomposed in situ, when feasible, by adding acid, base, oxidant, or reductant. Otherwise, the material should be concentrated to a minimum volume and added to the contents of a waste solvent drum. 

Figures 11(a) and 11(b) [112] show the variation of Ni-Ge-P deposition rate and Ge content as a function of aspartic acid and Ge(IV) concentration, respectively. A relatively low P content, ca. 1-2 at%, was observed in the case of films exhibiting a high concentration of Ge (> 18 at%). Like other members of its class, which includes molybdate and tungstate, Ge(IY) behaves a soft base according to the hard and soft acids and bases theory (HSAB) originated by Pearson [113, 114], capable of strong adsorption, or displaying inhibitor-like behavior, on soft acid metal surfaces. In weakly acidic solution, uncomplexed Ge(IV) most probably exists as the hydrated oxide, or Ge(OH)4, which, due to acid-base reactions, may be more accurately represented as [Gc(OH)4 nO ] ".

As discussed earlier, acid-base reactions are always nonpremixed. For example, a semi-batch reactor could initially be filled with base at concentration B0 and acid is added with concentration A0. Likewise, a continuous reactor could be run with two feed streams one for acid and one for base. For both of these examples, the degree of mixing between the acid stream and the rest of the reactor contents can be quantified by introducing the mixture fraction , which obeys... 

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