Sulfate solutions, absorption spectra

Although it presents an obstacle in practical applications, the photoanodic corrosion of colloids has often been used to obtain information about the interaction of dissolved compounds with the photo-produced charge carriers, as it was found that solutes can influence the rate of the dissolution. Both promoting and retarding effects were observed The rate of dissolution is readily followed by recording the decrease in the intensity of the absorption spectrum of the colloid upon illumination, or more precisely, by determining the yields of metal and sulfate ions in solution. 

The luminescence of macrocrystalline cadmium and zinc sulfides has been studied very thoroughly The colloidal solutions of these compounds also fluoresce, the intensity and wavelengths of emission depending on how the colloids were prepared. We will divide the description of the fluorescence phenomena into two parts. In this section we will discuss the fluorescence of larger colloidal particles, i.e. of CdS particles which are yellow as the macrocrystalline material, and of ZnS particles whose absorption spectrum also resembles that of the macrocrystals. These colloids are obtained by precipitating CdS or ZnS in the presence of the silicon dioxide stabilizer mentioned in Sect. 3.2, or in the presence of 10 M sodium polyphosphate , or surfactants such as sodium dodecyl sulfate and cetyldimethylbenzyl-ammonium... 

FIGURE 7.13 The absorption spectrum, visible region, of a copper sulfate solution. 

Students should take 0.2 ml of the commercially solution (around 2 mg) and centrifuge it to eliminate the ammonium sulfate solution. The pellet obtained should be dissolved in 2 ml of phosphate buffer (0.1 M, pH 7.5). The concentration of the solution should be 1 mg ml-1. Plot the absorption spectrum of LDH and measure its concentration at 280 nm using an extinction coefficient equal to 1 (mg/ml) 1 cm-1. 

The visible absorption spectrum of a solution containing a known concentration of nitrated protein is measured in a solution buffered at pH 9.0, and the absorbance at the maximum (near 428 nm) used to calculate the nitrotyrosine content ( 428nm for the nitrophenoxide ion is 4200). The tyrosine and nitrotyrosine content of the modified protein should also be determined by amino acid analysis. If the sum of these values does not add up to the tyrosine content of the unmodified protein, intra- or intermolecular cross-linking may have occurred. The amino acid analysis may also reveal whether other side-reactions have taken place. Particular attention should be paid to the half-cystine, cysteine, methionine, histidine and tryptophan contents of the modified proteins. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate offers a rapid and highly sensitive way of detecting products of intermolecular cross-linking. Such products are readily removed by gel filtration. 

The ether layer is washed successively with 5% hydrochloric acid, 5% sodium carbonate aqueous solution and water, and then dried over sodium sulfate. Upon evaporation of ether, the residue is subjected to fractional distillation in vacuo, thereby to yield 8.9 g. of N-methyl linseed oil fatty acid amide, B.P. 178-190° C./0.03 mm. Hg, I.R. 1,650 cm.-l. (I.R. means wave number of the infrared absorption spectrum.)... 

Shake for 1 minute, allow the layers to separate, and filter the chloroform extracts through separate filters of about 2 g of anhydrous granular sodium sulfate supported on pledgets of glass wool. Extract each aqueous layer with two additional 10 mL portions of chloroform, filtering and combining with the respective main extracts. Evaporate the chloroform solutions under reduced pressure to dryness, and dissolve each residue in 10 mL of carbon disulfide. The infrared absorption spectrum, determined in a 1-mm cell, of the solution obtained from the test specimen exhibits maxima only at the same wavelengths as that of the solution obtained from the Reference Standard (RS). 

Prepare two aqueous solutions which contain approximately 1000 ppm each of 1-octanesulfonic acid or sodium dodecyl sulfate (use whichever is available) and p-toluenesulfonic acid dissolved in distilled, deionized water (DDI). Transfer a portion of this solution into a quartz, rectangular cuvette and record the UV absorption spectrum for both organic compounds. Prepare a 100-ppm solution that contains methyl methacrylate and a 100-ppm solution that contains ethyl glycolate. You will need to use the wavelength cutoff guide to choose a suitable solvent because these organic compounds do not dissolve to any great extent in water. Record the UV absorption spectrum between 200 and 350 nm. Compare the spectra when a solvent is placed in the reference beam of the dual-beam instrument. 

Dissolve the appropriate methyl ester in methanol, and saponify as previously described for preparation of retinol from retinyl acetate After saponification, add water, and then acidify with dilute glacial-acetic acid make sure the solution is acidic to litmus paper. (In aqueous-alkaline solution, retinoid carboxylic acids remain as sodium salts, and are not extracted by organic solvents.) Extract the retinoid-carboxylic acid with diethyl ether two or three times (Note that hexane is not a good solvent for these polar retinoids.) Then wash the ether extract with water, and dry it over anhydrous sodium sulfate. Alternatively, if the volume is small, vortex and centrifuge the sample, remove any water, and evaporate the solvent The retinoid-carboxylic acids usually are obtained as yellow solids. Do not add any (not even a trace) HCl to 5,6-epoxy retinoids, because they instantaneously undergo isomerization to 5,8-epoxy retinoids, this change in structure is readily confirmed by the change m absorption spectrum (Table 1). 

Extracts of these fat samples were treated with sodium sulfate-concentrated sulfuric acid mixture and fuming acid by the method described by Schechter et al. 5) in order to separate the organic-chlorine compound from the fatty materials. An infrared spectrum from 7 to 15 microns on carbon disulfide solutions of the residues from the fat qualitatively identified the organic-chlorine compound as toxaphene. All the bands of toxaphene in this spectral region were plainly seen in the treated steer extract, whereas none of the absorption bands were visible in the untreated steer extract. 

After the completion of the reaction, the solution was acidified to a pH of 4 with 2N sulfuric acid, followed by the addition of 50 ml of water. The solution was then extracted several times with ether. The extractant was dried over magnesium sulfate and the solvent was removed by evaporation at reduced pressure. Cold petroleum ether was then added to the resultant oily material to precipitate the product. The product was further washed with cold (10° C) petroleum ether and recrystallized several times from warm petroleum ether. The melting point of the final product was 73.5° C. Infrared spectrum of the product showed major absorption peaks relevant to the pure monomer (Figure 1). Under UV radiation, white flakes of the monomer solid turned deep blue (partial polymerization). 

The maximum ultraviolet absorption of aqueous solutions of monopropiony1 erythromycin is at 285 nm. Monopropionyl erythromycin was used because propionyl erythromycin lauryl sulfate is practically insoluble. Murphy4 has reported that the ultraviolet spectrum of the esters of erythromycin are not significantly... 

The infrared spectrum of a sample of sulfated N-carboxymethyl chitosan insolubilized with acetone at pH 1.0 (hydrochloric acid) as well as a spectrum of sulfated N-carboxymethyl chitosan obtained by lyophilizing a solution of pH 8.3 show strong absorption bands at 1230 and 800 cm , assigned to the sulfate group they do not occur in the N-carboxymethyl chitosan spectrum (Fig. 2 of Ref,42). 

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