Weak organic acids

A weakly acidic organic acid. Extract into 10% NaOH-water solution. The strong base is needed to rip the protons out of weak acids (they don t want to give them up) and turn them into salts Then they ll go into the NaOH-water layer. 

Amal et al., 1992). A sample of dissolved organic matter from a swamp and also two weakly acidic, organic model compounds (polyaspartic and polyacrylic acid) induced a stable sol of hematite (60 nm particles) to form at pH 4.0 and 6.3, respectively (Tiller and O Melia, 1993). 

In sodium chloride solutions the ion transport number for Na+ is about 0.4 compared to about 0.6 for Cl . Thus a CX membrane would be expected to polarize at lower current densities than an AX membrane. Careful measurements show that CX membranes do polarize at lower current densities however, the effects on pH are not as significant as those found when AX membranes polarize. Such differences in behavior have been satisfactorily explained as resulting from catalysis of water dissociation by wealdy basic groups in the AX membrane surfaces and/or by weakly acidic organic compounds absorbed on such surfaces (5). 

Most weakly acidic organic chemicals are in a negatively charged form at the pH of most natural soils, while most weakly basic chemicals are in their non-ionized or molecular form. The Koc approach may still be applied to organic acids and bases, but it is necessary to consider the sorption of both ionic and neutral forms. For example, Fontaine et al. (1991)... 

P. Chu (Mobil Research Development Corp., Paulsboro, N. J. 08066) I am very interested in the way you prepared the H-Y sample. Why did weakly acidic organic exchange resins have to be used What degree of exchange can you achieve without damage to the zeolite structure How stable thermally is the final H-Y sample ... 

Many acids and bases, however, do not dissociate completely. Organic acids (compounds with carboxyl groups) do not completely dissociate in water. They are referred to as weak acids. Organic bases have a small but measurable capacity to combine with hydrogen ions. Many common weak bases contain amino groups. 

Chelate materials of this type are products of reaction of a metal base, such as calcium hydroxide or metal oxide, with weakly acidic organic substances with at least two functional groups. The ones used clinically are typically hydrolytically unstable, and this is responsible for their therapeutic effects. Ions released have beneficial properties, reducing inflanunation, being bacteriostatic and stimulating the odontoblasts to form secondary dentine. Ideally, calcium hydroxide chelates of this kind dissolve completely with time, and thus have the maximum possible therapeutic effect. 

The influence of acidic eluents on the retention behavior of anions and cations in ion-exclusion / cation-exchange chromatography was examined by a Japanese group [16]. Common inorganic anions and two weak-acid organic anions, as well as Na, NH4 and K, were separated on a carboxylic acid gel column in < 10 min with a weakly acidic aqueous eluent (Figure 8.5). 

It should be noted here that reactions in the presence of bases follow a slightly different mechanism involving deprotonation of moderately to weakly acidic organic compounds at the interface, as discussed further later in Chapter 16. 

Alkyds dimensional stability in regard to their mechanical and electrical properties are retained over wide temperature ranges. Alkyd parts will resist weak acids, organic solvents, and hydrocarbons such as alcohol and the fatty acids, but they are attacked by alkalis. 

A weak acid, HA, with a fQ of I.O X 10, has a partition coefficient, Rp, between water and an organic solvent of I20( What restrictions on the sample s pH are necessary to ensure that a minimum of 99.9% of the weak acid is extracted in a single step from 50.0 mF of water using 50.0 mF of the organic solvent ... 

A sample contains a weak acid analyte, HA, and a weak acid interferent, HB. The acid dissociation constants and partition coefficients for the weak acids are as follows Ra.HA = 1.0 X 10 Ra HB = 1.0 X f0 , RpjHA D,HB 500. (a) Calculate the extraction efficiency for HA and HB when 50.0 mF of sampk buffered to a pH of 7.0, is extracted with 50.0 mF of the organic solvent, (b) Which phase is enriched in the analyte (c) What are the recoveries for the analyte and interferent in this phase (d) What is the separation factor (e) A quantitative analysis is conducted on the contents of the phase enriched in analyte. What is the expected relative erroi if the selectivity coefficient, Rha.hb> is 0.500 and the initial ratio ofHB/HA was lO.O ... 

A 250.0-mg sample of an organic weak acid was dissolved in an appropriate solvent and titrated with 0.0556 M NaOH, requiring 32.58 ml to reach the end point. Determine the compound s equivalent weight. 

The acidity constant for an organic weak acid was determined by measuring its absorbance as a function of pH while maintaining a constant total concentration of the acid. Using the data in the following table, determine the acidity constant for the organic weak acid. 

In addition to the Hquid—Hquid reaction processes, there are many cases in both analytical and industrial chemistry where the main objective of separation is achieved by extraction using a chemical extractant. The technique of dissociation extraction is very valuable for separating mixtures of weakly acidic or basic organic compounds such as 2,4-dichlorophenol [120-83-2] and 2,5-dichlorophenol [583-78-8] which are difficult to separate by... 

Sulfonylurea herbicides ate weak acids and, in general, ate not strongly sorbed to soils. Sorption of chlotsulfuton and metsulfuron—methyl is inversely related to soil pH (407) and is positively correlated to soil organic matter (408). 

Collectors ndFrothers. Collectors play a critical role ia flotation (41). These are heteropolar organic molecules characterized by a polar functional group that has a high affinity for the desired mineral, and a hydrocarbon group, usually a simple 2—18 carbon atom hydrocarbon chain, that imparts hydrophobicity to the minerals surface after the molecule has adsorbed. Most collectors are weak acids or bases or their salts, and are either ionic or neutral. The mode of iateraction between the functional group and the mineral surface may iavolve a chemical reaction, for example, chemisorption, or a physical iateraction such as electrostatic attraction. 

In general, all iron pigments are characteri2ed by low chroma and excellent Hghtfastness. They are nontoxic, nonbleeding, and inexpensive. They do not react with weak acids and alkaHes, and if they are not contaminated with manganese, do not react with organic solvents. However, properties vary from one oxide to another. 

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