Extractable Acidity

Sample reading from standard curve = S Concentration of extractable Al from standard curve = C 

This fraction constitutes the hydroxy-Al monomers and polymers which are strongly adsorbed by soil colloid surfaces and behave as if they are virtually non-exchangeable. 

Non-exchangeable acidity = Extractable acidity - Exchange acidity. 

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Step 1. Extraction and separation of the acidic components. Shake 5-10 g. of the sohd mixture (or of the residue R obtained after the removal of the solvent on a water bath) with 50 ml. of pure ether. If there is a residue (this probably belongs to Solubihty Group II or it may be a polysaccharide), separate it by filtration, preferably through a sintered glass funnel, and wash it with a Uttle ether. Shake the resulting ethereal solution in a smaU separatory funnel with 15 ml. portions of 5 per cent, aqueous sodium hydroxide solution until all the acidic components have been removed. Three portions of alkaU are usuaUy sufficient. Set aside the residual ethereal solution (Fj) for Step 2. Combine the sodium hydroxide extracts and wash the resulting mixture with 15-20 ml. of ether place the ether in the ETHER RESIDUES bottle. Render the alkaline extract acid to litmus with dilute sulphuric acid and then add excess of sohd sodium bicarbonate. 

A.cidic Extractants. Acidic extractants, HE, react with REE according to a cation-exchange reaction ... 

These can be purified by extracting acidic and basic impurities with aqueous base or acid, respectively. However, they are somewhat sensitive to strong alkali which slowly cleaves the disulfide bond. TTie lower-melting members can be fractionally distilled under vacuum. The high members can be recrystallised from alcohol, toluene or glacial acetic acid. 

Amine Guard A process for extracting acid gases from refinery streams by scrubbing with an alkanolamine. Many such processes have been developed, this one was developed by the Union Carbide Corp. and uses monoethanolamine. It has been used to purify hydrogen produced by steam reforming. In 1990, over 375 units were operating. 

LAS Sludge-amended soil Microwave extraction (acidic methanol) SAX + RP-C8 HPLC-FL [Pg.833]

Potable water and raw source water Sample acetylated in situ by addition of acetic anhydride, solvent extracted and concentrated alternatively, extracted acidic sample derivatized by pentafluorobenzyl bromide and cleaned up by column chromatography HRGC-ECD (for pentafluorobenzyl derivative) HRGC-MS (for acetyl derivative) <50 ng/L (pentafluorobenzyl) <50 ng/L (acetyl derivative) 10-64% (pentafluorobenzyl derivative) 70-132% (acetyl derivative) Sitholeetal. 1986... 

Determination of Endothall in Drinking Water by Ion-Exchange Extraction, Acidic Methanol Methylation, and... 

The extraction of most acids is accompanied by extraction of water. In the extraction of HNO3 by TBP into kerosene, many different species have been identified, several of which involve hydration. The ratio of acid adduct is not very predictable. For example, HCIO4 apparently is extracted into kerosene with 1-2 molecules of TBP, HCl into ethylether with one molecule of ethylether, etc. Also, the extracted acid may dimerize in the organic solvent, etc. Example 2 illustrates the complexity of the extraction of HNO3 by TBP into kerosene. 

According to Eq. (4.74) Aex increases to the z power of the dissociation constant, A a, for the extractant acid HA. Thus it appears desirable to use stronger acids as extractants, i.e., those with large (or small pATa). Thus factors that affect the dissociaton constant of an acid are of importance for extraction behavior. 

Caustics are widely used in petroleum refineries. Typical uses are to neutralize and to extract acidic materials that may occur naturally in crude oil, acidic reaction products that may be produced by various chemical treating processes, and acidic materials formed during thermal and catalytic cracking such as H2S, phenolics, and organic acids. 

The data above enable us to make some rough estimates of costs associated with two processes (i) ACID, that is aspen wood-autohydrolysis-caustic extraction-acid hydrolysis-fermentation-distillation and (ii) ENZYME, that is aspen wood-autohydrolysis-caustic extraction-enzymatic hydrolysis-fermentation-distillation. For purposes of comparison, the product in both cases will be assumed to be 10 million gallons of 95% ethanol per year, a minimum economic size. 

Approximately 40 to 50% of the total amount of phenolics sorbed was retained by the organic matter fraction (27). In surface soil layers, organic matter is frequently intimately associated with the mineral components present, providing a large surface area and reactive sites for surface interaction. Soil acidity has a major influence on phenolic adsorption by the organic carbon fraction, since the degree of dissociation of the phenolic acids is pH-dependent. Whitehead and coworkers (28) observed that the extractability of several phenolic acids was highly dependent upon the extractant pH between pH 6 and 14. The amount extractable continually increased with extractant pH thus the extracted acids could not be readily classified into distinct fractions. 

Extract acid from the fuel with a mild caustic solution. Check pH of extracted water to ensure that the acid has been removed. 

Extract acidic components from fuel with distilled water and check for decrease in pH. 

Alkaline-extracted/acid hydrolysis (AH/NaOH) lignin samples were prepared by subjecting aspen wood flour to a one hour cook at 120°C in 0.05N sulfuric acid (22), followed by mixing the clarified supernatant with 1% w/w NaOH at 25°C with a Waring blender. The insoluble lignins were precipitated by addition of acid and water washes (32% yield). 

Tho brown extractive acid requires further investigation. It is probably a mixture of different matters, and, perhaps, a product of alteration. 

To extract acid dissociation constants from an acid-base titration curve, we can construct a difference plot, or Bjerrum plot, which is a graph of the mean fraction of bound protons, H, versus pH. This mean fraction can be measured from the quantities of reagents that were mixed and the measured pH. The theoretical shape of the difference plot is an expression in terms of fractional compositions. Use Excel SOLVER to vary equilibrium constants to obtain the best fit of the theoretical curve to the measured points. This process minimizes the sum of squares [nH(measured) -nH( theoretical) 2. 

Extraction with a mixture of CH2C12, ethylacetate, MeOH, and NH4OH. Decantation, filtration, evaporation to dryness. Ether-MeOH dissolution, HC1 extraction. Acid layers washed with hexane, basified, LLE in CH2C12. Organic extract evaporated, dissolved in MeOH, and filtered. 

By increasing the ionic strength, that is, the acid or metallic salt concentration, in the aqueous phase, the concentration of the extracted acid or salt in the organic phase increases and induces an increase in the attractions between reverse micelles (see below). Numerically, all the terms can be evaluated (7, 37, 83). It can then clearly be concluded that this effect is the origin of the third-phase formation. 

To recover the p-xylene, the ether is evaporated and the p-xylene distilled. In the case of p-toluidine and p-methylphenol, once the product is liberated from the corresponding salt, it is extracted from the water by ether. The ether is then evaporated and the desired product is distilled. The order of extraction—acid first, then base—can be reversed. 

Exposure to toluene can be detected by extracting hippuric acid from acidified urine into diethyl ether or isopropanol and direct ultraviolet absorbance measurement of the extracted acid at 230 nm. When the analysis is designed to detect xylenes, ethylbenzene, and related compounds, several metabolites related to hippuric acid may be formed and the ultraviolet spectrometric method does not give the required specificity. However, the various acids produced from these compounds can be extracted from acidified urine into ethyl acetate, derivatized to produce volatile species, and quantified by gas chromatography. 

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