Standard ethanol-water

In at least one case, the standard Bucherer-Bergs conditions gave rise to oxazole rather hydantoin. Specifically, when 5-benzyloxy-pyridine-2-carbaldehyde (11) was treated with potassium cyanide, ammonium chloride, and ammonium carbonate in boiling ethanol/water, 5-amino-oxazol-2-ol 12 was obtained. Subsequent heating of oxazole 12 with acetic acid at reflux overnight then produced the Bucherer-Bergs product, hydantoin 13. ... 

Procedure. Weigh out accurately about 4 g of the pure organic acid, dissolve it in the minimum volume of water (Note 1), or 1 1 (v/v)ethanol/water mixture, and transfer the solution to a 250 mL graduated flask. Ensure the solution is homogeneous and make up to the required volume. Use a pipette to measure out accurately a 25 mL aliquot and transfer to a 250 mL conical flask. Using two drops of phenolphthalein solution as indicator, titrate with standard 0.2M (approx.) sodium hydroxide solution (Note 2) until the colourless solution becomes faintly pink. Repeat with further 25 mL volumes of the acid solution until two results in agreement are obtained. 

Bergeron, C. et al.. Comparison of the chemical composition of extracts from Scutellaria lateriflora using accelerated solvent extraction and supercritical fluid extraction versus standard hot water or 70% ethanol extraction, J. Agric. Food Chem., 53, 3076, 2005. 

Identification of dyes on dyed textiles is traditionally carried out by destructive techniques [493], TLC is an outstanding technique for identification of extracted dyestuffs and examination of inks. Figure 4.9 shows HPTLC/SERRS analysis of acridine orange [492], Wright et al. [494] have described a simple and rapid TLC-videodensitometric method for in situ quantification of lower halogenated subsidiary colours (LHSC) in multiple dye samples. The results obtained by this method were compared with those obtained by an indirect TLC-spectrophotometric method and those from HPLC. The total time for the TLC-videodensitometric assay of five standards and four samples applied to each plate was less than 45 min. The method is applicable for use in routine batch-certification analysis. Loger et al. [495,496] have chromatographed 19 basic dyes for PAN fibres on alumina on thin-layer with ethanol-water (5 2) and another 11 dyes on silica gel G with pyridine-water... 

Ninhydrin assay. Our method to determine reactivity towards ninhydrin was a modification of a method described previously (Moore and Stein, 1954 Moore, 1968). Briefly, dried samples were dissolved in 0.10 ml 0.1 M acetic acid and mixed with an equal volume of ninhydrin reagent (Sigma). After 15 minutes in a boiling water bath, samples were diluted with 0.80 ml ethanol/water (1 1 by vol.) and measured for absorbance at 550 nm on a flow-through spectrophotometer (Vitatron). Standards containing 0-0.6 mM leucine in 0.1 M HAc were included. Values were therefore calculated as leucine-equivalents. 

The use of ISEs in non-aqueous media(for a survey see [125,128]) is limited to electrodes with solid or glassy membranes. Even here there are further limitations connected with membrane material dissolution as a result of complexation by the solvent and damage to the membrane matrix or to the cement between the membrane and the electrode body. Silver halide electrodes have been used in methanol, ethanol, n-propanol, /so-propanol and other aliphatic alcohols, dimethylformamide, acetic acid and mixtures with water [40, 81, 121, 128]. The slope of the ISE potential dependence on the logarithm of the activity decreases with decreasing dielectric constant of the medium. With the fluoride ISE, the theoretical slope was found in ethanol-water mixtures [95] and in dimethylsulphoxide [23], and with PbS ISE in alcohols, their mixtures with water, dioxan and dimethylsulphoxide [134]. The standard Gibbs energies for the transfer of ions from water into these media were also determined [27, 30] using ISEs in non-aqueous media. 

Figure 11. The influence of residual H2O2 on the reaction testing of phenol hydroxylation to catechol (CAT), hydroquinone (HQ), and para-benzoquinone (BQ) [61], Reaction conditions 4 g phenol 50 mL water solvent 0.2 g a-Fe203 catalyst inner standard ethanol reaction temperature 70°C. Aliquots were sampled at different times and analyzed by (a) HPLC and (b) GC to determine the conversions of PHE (A) and yields of CAT + HQ + BQ ( ), CAT ( ), and BQ (T). Aliquots were also analyzed by (c) iodometric titration to determine the conversion of H2O2 (o). [Reproduced by permission of Elsevier from Ma, N. Ma, Z. Yue, Y. H. Gao, Z. J. Mol. Catal. A 2002, 184, 361-370.]...

Pierson s Procedure D-4- Water Extraction (Ref 11, pi357 Ref 17, Method D9Q-4). Distilled water is used for extracting the residue from the ether soluble determination. Compare with BurMines Standard Method No 32 in which extraction is done with 1 1 ethanol-water soln. (See also Section III, steps 1 to 3, of this work)... 

For the hydrolysis reactions, five different components make up the reaction mixture the silane, water, acid, ethanol (to solubilize the water) and mesitylene (the internal standard). The water, acid, ethanol and mesitylene were weighed (to 0.001 g) into the vial, which was then sealed with the polypropylene cap. The vial was placed in a constant temperature bath and allowed to reach equilibrium (approximately 30 min). The silane to be used was kept in the constant temperature bath as well. The reaction was initiated by removing the reaction vial from the bath, quickly weighing in the desired amount of the silane, mixing the solution momentarily with a Vortex-Genie and then returning it to the bath. 

For blanks one can use ethanol, water or methanol, whichever the tissue extract was dissolved in last. Since this is a spectrophotometric assay, it is important to have a standard curve to relate the absorbance value to a concentration. Common compounds used to generate a standard curve are chlorogenic acid (1.18) or gallic acid (1.5). The concentration of phenolic compounds is then reported as chlorogenic acid or gallic acid equivalents, respectively. 

A method has been developed for calculating equilibrium vapor compositions, based on boiling point vs. liquid composition data, for systems saturated with a salt. Such ternary systems in effect have been treated as binaries (26) in which the standard state of each of the two liquid components is that of being saturated with salt instead of being pure and with the pure-component vapor pressures being so adjusted. For example, in the ethanol-water-salt ternary systems tested, they have been considered as binaries composed of water saturated with salt as one component and ethanol saturated with salt as the other component. In the testing to which it has been subjected so far, the method seems encouraging. 

Preparation for Bioassav. The standard in vitro assay for allatostatins (1) is a two hour organ culture of corpora allata during which the inhibition of release of radiolabeled JH III from [ H-methyl] methionine is measured accordingly, the test sample must be free from unphysiological contaminants before incorporation into the modified tissue culture medium 199 (1). Our preparative-scale procedures all involved volatile modifiers (hydrochloric acid, formic acid, ammonium formate, TFA) which could be removed along with the solvents (ethanol, water, acetonitrile) this analytical workup of aliquots for bioassay was the only occasion when we used vacuum evaporation. 

The k standard deviation data and R.A.A.D. values listed in Table VIII for the data of the present investigation and certain data from previous studies (3,4) demonstrate clearly that Equation 1 can satisfactorily correlate the salt effects of the inorganic salts tested at fixed-liquid composition in ethanol-water, at all salt concentrations up to saturation. The R.A.A.D. yields a critical evaluation of the applicability... 

Table III contains the experimental quantities (except the potential, E) and the constants used to determine the standard potentials of the cell (Equation 3). The ion-size parameter a for water and terf-butanol-water solvents is 5.50 A, and for ethanol and ethanol-water it is 5.00 A.

No comparison exists for the standard potentials in terf-butanol-water mixtures or in anhydrous tert-butanol. However, the trends in the data obtained here in terf-butanol are similar to the trends observed in this work in ethanol-water and in anhydrous ethanol. See Figures 1 and 2 in which the standard potentials E° for the silver-silver bromide elec-... 

Table III. Experimental Quantities Except the Potential E and the Constants Used in Calculating the Standard Potentials ° of the Cell in Equation 3. Radius is 5.00 A for Water, Ethanol and Ethanol—Water and 5.50 A for tert-6 Butanol and tert-Butanol—Water Solvent...

Figure 1. Standard potentials of the cell Ft, H2 HBr(m), X% alcohol, Y% water AgBr-Ag in ethanol-water (radius = 5.00) ( ), 25°C (O),...

GAF Corp., respectively. These surfactants were used without further purification. Sodium dodecylsulfate (SDS), obtained from Fisher Scientific Co., was purified by recrystallization from an ethanol-water mixture. 4-dodecyl-diethylenetriamine (DDIEN) was purchased from Eastman Kodak Co. Metal ion salts were all reagent grade. Standard pH buffers (Fisher Scientific Co.) and Hepes buffers (Sigma Chemical Co.) were used as provided. 

Incubate the probe/dithiothreitol (DTT 0.1 M DTT in water) solution (purchased from Sigma-Aldrich, Product 43816) at room temperature for 30min, followed by removal of the DTT using a standard ethanol precipitation procedure. Determine the concentration of DNA solution and adjust it to 25 pM (make the... 

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