Standards aqueous

Solutions of Mn04 are prepared from KMn04, which is not available as a primary standard. Aqueous solutions of permanganate are thermodynamically unstable due to its ability to oxidize water. 

One example of a liquid-based ion-selective electrode is that for Ca +, which uses a porous plastic membrane saturated with di-(n-decyl) phosphate (Figure 11.13). As shown in Figure 11.14, the membrane is placed at the end of a nonconducting cylindrical tube and is in contact with two reservoirs. The outer reservoir contains di-(n-decyl) phosphate in di- -octylphenylphosphonate, which soaks into the porous membrane. The inner reservoir contains a standard aqueous solution of Ca + and a Ag/AgCl reference electrode. Calcium ion-selective electrodes are also available in which the di-(n-decyl) phosphate is immobilized in a polyvinyl chloride... 

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. 

IQ. To determine the concentration of chloride ion, - a 5-mL aliquot of the methyl lithium solution is cautiously added to 25 ml of water and the resulting solution is acidified with concentrated sulfuric acid and then treated with 2-3 ml of ferric ammonium sulfate [Fe(NH4)( 04)2 12 H2O] indicator solution and 2-3 ml of benzyl alcohol. The resulting mixture is treated with 10.0 mL of standard aqueous 0.100 M silver nitrate solution and then titrated with standard aqueous 0.100 H potassium thiocyanate solution to a brownish-red endpoint. 

As mentioned in Sec. 90 we may think of this AS0 as being the difference between the molar entropy of solid 1 j2C03 and the partial molal entropies of one (C03) ion and two Lif ions, each in its hypothetical standard aqueous solution. We propose now to compare the AS of the reaction... 

Solutions containing approximately 1.6JH butyllithium in hexane were purchased either from Alfa Inorganics, Inc., or from Foote Mineral Company, The concentration of butyllithium in these solutions can be determined either by a double titration procedure2 or by dilution with anhydrous tetrahydro furan followed by titration with 2-butanol in the presence of a 2,2 -bipyridyl indicator.3 In either ease the total base concentration in the reagent is determined by titration with standard aqueous acid. 

Bet de Bethune, A.J., Swendeman Loud, N.A. Standard Aqueous Electrode Potentials and Temperature Coefficients at 25 °C, Skokie C.A. Hampel, 1964. 

Bis-derivitisation with fluorescamine and HPLC with fluorescence detection Aqueous simulants — HPLC with fluorescence detection. Olive oil extracted with methanol /water after addition of hexane Aqueous simulants — HPLC with UV detection. Olive oil extracted with 80% aqueous acetonitrile Headspace GC with FID detection and pentane internal standard Aqueous simulants GC. Olive oil extracted with water/ethanol and GC detection... 

The sparingly water-soluble triethylammonium saltofBi2H122-is readily converted to the highly water-soluble sodium salt. A carefully weighed sample of the triethylammonium salt is treated with an exactly equivalent amount of standardized aqueous sodium hydroxide. The mixture is heated to effect solution and then boiled to expel the free triethylamine until the vapors are no longer basic. Evaporation to dryness then leaves a crystalline hydrate of Na2Bi2Hi2. The anhydrous salt is obtained by drying at 100°/1 n for 24 hours and has characteristic infrared absorption frequencies as a Nujol mull (exclusive of any frequencies coincident with Nujol) at 2470 (s), 1010 (w), 1070 (m), 770 (w), 727 (m),710 (m),and 700 (m) cm. 1... 

The [1,4]-Wittig rearrangement is potentially useful not only for the carbon-carbon bond formation but also for enolate formation. However, synthetic applications have been rather limited, because of the low yields and restricted range of substrates. Schlosser s group have developed a practical approach to aldehydes based on a [1,4]-rearrangement/ enolate trapping sequence. In contrast, standard aqueous workup gave poor yield of aldehyde. This protocol was employed as the key step in a synthesis of pheromone (102) from 99 via 100 and 101 (equation 56f. ... 

A. J. de Bethune, N. A. Swendeman Loud, Standard Aqueous Potentials and Temperature Coefficients at 25°C., Hampel, Skokie,... 

The standard aqueous redox chemistry of vanadium and the other group 5 elements is summarized in the Latimer diagrams shown in Fig. 1 [2]. Under standard acidic aqueous conditions, the stability of the -1-5 oxidation state increases for the heavier group 5 elements at the expense of the +4 and -L3 states. 

Lactobacillus kefir (ADH E.C. 1.1.1.1) for use in organic solvents [11, 12]. Both biocatalysts are characterized by a very low stability in pure organic solvents or standard aqueous-organic two-phase systems [20], though their broad substrate ranges include many hydrophobic compounds [21, 22]. Figure 3.2.2 illustrates the denaturation of native BAL at the interface between a buffered aqueous solution and octanone. 

The KOH is ground with a mortar and pestle in a fume hood, and the ether is used as supplied. The submitters noted that when very dry KOH and ether were used, the reaction did not proceed to completion. They then effected the reaction with 50% aqueous KOH solution instead of powdered KOH, followed by a standard aqueous workup. 

In standard aqueous media, hydrolases are enzymes which are able to hydrolyse covalent bonds (Fig. 1). Three classes of hydrolases are used industrially osidases (glycosidic linkage hydrolysis), proteinoses (peptidic linkage hydrolysis) and esterases (ester linkage hydrolysis). 

Scheme 44 summarizes an addition reaction by the Barton method. Thiohydroxamate esters (32) are readily prepared and isolated, but, more typically, they are generated in situ. Experimental procedures have been described in detail148151 and often entail the slow addition of an acid chloride to a refluxing chlorobenzene solution of the readily available sodium salt (31), dimethylaminopyridine (DMAP, to catalyze the esterification), and excess alkene. The products are usually isolated by standard aqueous work-up and chromatographic purification. 

The concentration of diazomethane may be determined by reaction of an aliquot of the ethereal solution with a weighed excess of benzoic acid in cold (0°) ether solution as described in an earlier volume of this series.3 The unchanged benzoic acid is then determined by titration with standard aqueous 0.1 M potassium hydroxide. 

Subsequent attempts to repeat this work failed. Instead, reaction of 3-pbenyl-5-isoxazolone with POCI3/DMF, first at room temperature then for 30 minutes at 60°C, gave the isoxazolone 4 in 35% yield after standard aqueous quench and neutralisation with 5% NaHC03 solution. When longer reaction times were employed, or when the reaction temperature was raised to 80°C, the product, isolated in 71% yield, was the 1,3-oxazinone 5, and 4 was shown to be the precursor to 5. 

Mydriatic activity on rabbits and humans, and cycloplegic activity on humans were tested. It was found that tropicamide bioavailability, both in rabbits and in humans, was not decreased by micellar solubilization. The conclusion was that some poloxamers perform satisfactorily as solubilizing vehicles for tropicamide, producing neutral 1.0-1.5% drug solutions that are better tolerated and more effective than the standard aqueous eyedrops. 

The membrane perm-selectivity (y.m) is defined as the ratio between the actual and theoretical transfer of counterions through any IEM. It can be simply determined as the percentage ratio between the experimental and theoretical Donnan potential differences as measured using a test system consisting of two cells provided with calomel electrodes and filled with well-mixed standardized aqueous solutions of KC1 (at 0.1 and 0.5 kmol/m3), kept at 25 °C, and separated by the IEM sample under testing. 

Reagents. Give the structure of the major products (A-G) expected from the following reactions. Assume standard aqueous workup conditions are used for product isolation. 

The peak height of Be(TFA)2, at a retention time of 1.9 min, was taken for the quantitative determination of beryllium as shown in Fig. 15.12 (a). In the chromatogram (Fig. 15.12 (b)) the solvent peak of cyclohexane (retention time ca. lmin) was a tailing that resulted from incomplete removal of free HTFA, in which a random determination would be obtained. The calibration curve of Be(TFA)2 was obtained from the measurement of standard aqueous solutions or standard solutions of Be(TFA)2 in cyclohexane. 

The aldehyde (0.38 mmol, 1.5 equiv), the catalyst (10 mol%), and benzoic acid (10 mol%) were stirred in toluene and cooled to —15 °C. The thiol (1 equiv) was added and the reaction mixture stirred for 30 min. Diazo dicarboxylate derivative (1.3 equiv) was added and the reaction progress monitored by TLC (3-24 h). The crude reaction mixture was diluted with MeOH (2 mL) and cooled to 0 °C, followed by the addition of NaBH4 (2 equiv). After 10 min, 2 M NaOH (2 mL) and THF (2 mL) were added and the crude reaction mixture was stirred for 2 h. After standard aqueous work-up, the product was purified by FC on silica gel. 

Any aqueous waste, such as dissolution media, that is generated should also be evaluated on a case-by-case basis. Potent compounds are normally dosed in formulations containing milligram or lower levels of active compound. Dissolution or other aqueous wastes are therefore normally very dilute solutions. As long as there are no ecological toxicity issues, dissolution media and aqueous wastes containing potent compounds can normally be incorporated into the standard aqueous waste stream. If there are any toxicity issues associated with the wastes, the aqueous wastes and dissolution media should be segregated from the normal waste stream and treated in an appropriate manner. 

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