Base extraction acid neutralization

Bioavailable trace elements in soil correlate with plant uptake and concentrations in plants. Extractants for bioavailable trace elements include chelating agents, diluted inorganic acid, neutral salt solutions, and water (Table 7.2). The most popular extractant for bioavailable trace elements in arid and semi-arid soils is DTPA-TEA (triethanolamine), which was developed by Lindsay and Norvell (1969, 1978) to extract available Cu, Zn, Fe and Mn from neutral and calcareous soils. Use of this chelating agent, DTPA, is based on the fact that it has the most favorable combination of stability constants for simultaneous complexation of Cu, Fe, Mn and Zn... 

A closely related synthesis utilizes alkynic epoxides, which add hydrogen sulfide in the presence of a base to form thiophenes in good yield. For example, when the epoxide (184) was stirred in an aqueous solution of barium hydroxide with slow addition of hydrogen sulfide gas, and the product extracted after neutralization with acetic acid, the substituted thiophene (186) was obtained in 60-70% yield (53ZOB1569). In these experiments R1 = Me or Et, R2 = H or Me and R3 = Ph. The same synthetic method was used to produce a thiophene having an optically active substituent, with relatively little racemization. In this case R1 = EtC HMe while R2 and R3 = H, but the yield was equivalent (73JOC2361). This reaction also undoubtedly proceeds via an intermediate (185), a structure related to a 1 -mercapto-1,3-butadiene. 

Wipe and liquid samples from pyrolized transformer oil (CDDs) Extraction with organic solvent and washing of organic layer sequentially with base and acid separation on neutral silica gel clean-up and fractionation on carbon/silica column HRGC/LRMS No data 83-134 (wipe) 19-70 (liquid) Hardin et al. 1989... 

A general extraction scheme (Figure 2.16) can be devised to extract semivolatile organics from aqueous solution such that important categories of organic compounds (i.e., bases, weak acids, strong acids, and neutrals) are fractionated from each other and isolated in an organic solvent. Many... 

A benzene solution of 2.2 parts of a-chloro-y-quinoline-carboxylic acid chloride is gradually mixed, while cooling, with 2.3 parts of unsymmetrical diethylethylenediamine. When the reaction is at an end the solution is washed with water and the new base extracted by means of hydrochloric acid. The base is precipitated by means of sodium carbonate and extracted with benzene. The solvent is distilled and the base recrystallized from petroleum ether. The a-chloro-y-quinoline-carboxylic acid diethyl-amino-ethylene amide forms colorless lamina crystals of melting point 74°C. With acids the base forms neutral salts soluble in water. 

Meat extracts satisfied the immediate needs but they became in short supply. A Swiss chemist by the name of Julius Maggi developed a meat type flavoring product based on acid hydrolysis of plant protein. When such materials are neutralized and reduced to paste or powder by heat they acquire a flavor profile useful as a meat extract substitute. Today the market for that product, called Hydrolyzed Vegetable Protein or HVP, is more than 300 million world wide (1). HVP represents the first modern commercial example of the use of heat to develop a useful material for its use as a flavoring. 

Displacement of the bromide by cyanide ion, using the copper (I) salt as the nucleophile, gives a mixture of nitriles in which the more stable primary nitrile predominates even more. These can be separated by a clever device. Hydrolysis in concentrated HCl is successful with the predominant primary nitrile but the more hindered secondary nitrile does not hydrolyse. Separation of compounds having two different functional groups is easy in this case the acid can be extracted into aqueous base, leaving the neutral nitrile in the organic layer. 

Further purification of the total lipid extract from neutral lipids like triacylglycerols is desirable to increase the separation performance and lifetime of reverse-phase HPLC columns. Several authors have utilized a procedure of base-acid wash for this purpose (Evershed et al., 1988 Seitz, 1989 Hakala et al., 2002), where one takes advantage of the phenolic nature of the steryl femlates. Total lipid extract in acetone or... 

Vacuum-still bottoms from the H-coal liquefaction process were separated into acid, neutral, and basic fractions by precipitation with acids or by extraction with bases. About one-third of the preasphaltene and one-sixth of the asphaltene fraction were precipitated by acids equivalent weights of the bases were in the range 1200-1800 for preasphaltenes and 600-800 for asphaltenes. The acidic components were obtained either by extraction with aqueous sodium hydroxide or by extraction with benzyltrimethylammonium hydroxide in methanol. About one-fifth of the asphaltene and one-fourth of the presasphaltene fractions were obtained as acids, and up to 10% as amphoteric substances. Nitrogen and sulfur were present in all fractions found. Deno axidation (CF3C02H, H202, H 04) gave dicarboxylic acids from malonic to adipic in addition to mono acids. 

Acid-base extraction where covalent molecules are converted into their salts and thus removed from a non-polar solvent into water, while neutral covalent species will remain in the non-polar solvent, as shown in Table 14.1. 

Separation Techniques. The complexity of the organic composition of coal-derived liquids, shale oil, and their related effluents presents a formidable challenge to the analytical chemist. Our approach to this problem has been the classical separation technique based on acid-base-neutral polarity of the organic compounds. We further subdivide the neutral fraction into aromatic and non-aromatic fractions using dimethyl-sulfoxide (DMSO) extraction. DMSO effectively removes multiringed aromatic compounds with great eflBciency (85-95%) for these complex mixtures and thus allows a straightforward analysis for polynuclear... 

Often, from the point of view of electrolysis, the choice of electrolyte or solvent is free within certain limits, and the workup may then be facilitated considerably by a suitable selection of experimental conditions. For example, the reduction of a nitroalkane [50] to a hydroxylamine requires an aqueous acid medium sulfuric acid is just as good as hydrochloride acid for the electrolysis, but whereas hydrochloric acid may be removed in vacuo at a low temperature, leaving an alkylhydroxylamine hydrochloride, the sulfuric acid must be neutralized and the free, less stable base extracted. 

From the knowledge of the extractant characteristics of both neutral and mono-acidic phosphorus-based organic compounds now available, it is possible to tailor-make extractants for a specifically desired separation of two metals. The present study is concerned with neutral mono-nuclear, phosphorus-based extractants for use in affecting the mutual separation of U(VI) and Th(IV). 

Experimental studies were therefore directed to investigate the removal of actinides from both diluted (5000 l/t) and concentrated (about 500 l/t) HAW solutions. Three alternative processes have been selected for this purpose. They all rely upon actinide separation at low acidity conditions requiring a preliminary denitration step. Two of them (TBP and HDEHP processes) are based on solvent extraction techniques using as extractants a neutral (TBP) and an acidic (HDEHP) organophosphorus compound respectively. The third process (OXAL) applies as the first step the precipitation of actinides and lanthanides FP as oxalates. 

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