Residual salt analysis

Strontium isotope analyses. Strontium isotope data obtained using residual salt analysis (SrRSA) are the Sr/ Sr isotope ratios of residual salts extracted from reservoir cores (see Mearns McBride 1999 for a description of the methodology). The Sr/ Sr isotope ratios of formation waters are modified by diagenesis (water-rock interactions) and/or hydrodynamic processes through time. Once established, differences in the strontium isotope ratio will tend to... 

Formation water composition data derived from water and elemental residual salt analysis... 

It was felt that the presence of residual salts in the clay would complicate the analysis of experimental data. Therefore, in order to remove such salts prior to using the clay, the samples of sediment were dialyzed (using deionized water) until a twentyfold concentration of the dialyzing solution did not yield a precipitate upon addition of silver nitrate. (Also, no precipitate was observed upon concentration of the solution.) The solids were then dialyzed once more, vacuum dried, and stored in sealed containers in a desiccator until needed. (The preceding procedure may have resulted in some alteration of the sorption properties of the red clay, particularly with regard to the hydrous oxides. It is intended to assess the extent of such alteration, if any, during the course of future work.)... 

After about 3 hours or after analysis has indicated that the peroxide has been consumed (Note 5), the formic acid is removed by distillation under reduced pressure (b.p. 50°/125 mm.) in a stream of gas (carbon dioxide or nitrogen) to prevent bumping (Note 6). The residue in the flask, which consists of hydroxy-formoxystearic acids, is heated for 1 hour at 100° with an excess of 3N aqueous sodium hydroxide, and the hot, amber-colored soap solution is cautiously poured into an excess of 3N hydrochloric acid with stirring. The oil which separates is allowed to solidify, and the aqueous layer is discarded. The tan-colored solid is remelted on the steam bath by addition of hot water and stirred well to remove residual salts and water-soluble acids (Note 7). When the oil has solidified, the aqueous layer is discarded, and the solid is broken into small pieces and dissolved in 400 ml. of 95% ethanol by heating on the steam bath. After crystallization at 0° for several hours, the product is collected on a filter and dried under vacuum. The yield of crude 9,10-dihy-droxystearic acid is 75-80 g., m.p. 85-90°. After a second recrystallization from 250 ml. of 95% ethanol, the product weighs about 60-65 g. and melts at about 90-92°. A third recrystallization may be necessary to produce a pure product melting at 94-95°. The over-all yield is 55-60 g. (50-55%, based on the available oleic acid) (Note 8). 

Catalysts. The starting material for all the catalysts was Linde 13X in powder form, free of clay binder. The bulk sample had a silicon-to-aluminum ratio of 1.27 dz 0.02 16). In all cases, the zeolites were prepared by ion exchange with salt solution (either chloride, sulfate, or nitrate) of the required cation at room temperature. The extent of exchange was estimated from either analysis of the residual salt solution or determination of the residual sodium in the zeolite sample. After preparation, the exchanged zeolites were stored over saturated calcium nitrate solution. 

Figure 2.14 shows the overlapped FTIR spectra for pure PCL (a), electrospun PCL fibers (b) spun with 5% pyridine, and pyridinium acetate (c). The latter has two characteristic peaks at 1437 and 1580 cm representing, respectively, the C-N and C-C stretching vibrations. The electrospun PCL spectrum does not show peaks at these frequencies, suggesting that no residual salt remained in the fibers. The absence of pyridinium in the extrudate was confirmed by elemental analysis that showed that no extra nitrogen was present in the product. 

In similar circumstances, silver salts leave a residue of metallic silver lead and copper salts usually leave a residue of the corresponding oxide calcium and barium salts leave a resirlne of the carbonate or oxide. Identify the metal in all such cases by the usual tests of qualitative inorganic analysis. Metals other than the above are seldom encountered in elementan qualitative analysis. 

The silver salts of most carboxylic acids are only sparingly soluble in cold water, and hence are readily prepared. Moreover they very rarely contain water of crystallisation, and therefore when dried can be analysed without further treatment. The analysis itself is simple, rapid and accurate, because gentle ignition of a weighed quantity of the silver salt in a crucible drives off the organic matter, leaving a residue of pure metallic silver. 

The combination of oxidi2ing effect, acidic strength, and high solubiHty of salts makes perchloric acid a valuable analytical reagent. It is often employed in studies where the absence of complex ions must be ensured. The value of wet ashing techniques, in which perchloric acid is used to destroy organics prior to elemental analysis for the determination of trace metals in organics, has been well estabHshed (see Trace and residue analysis). 

Polypeptide Synthesis and Analysis. Sihca or controUed-pore glass supports treated with (chloromethyl)phenylethyltrimethoxysilane [68128-25-6] or its derivatives are replacing chloromethylated styrene—divinylbenzene (Merrifield resin) as supports in polypeptide synthesis. The sdylated support reacts with the triethyl ammonium salt of a protected amino acid. Once the initial amino acid residue has been coupled to the support, a variety of peptide synthesis methods can be used (34). At the completion of synthesis, the anchored peptide is separated from the support with hydrogen bromide in acetic acid (see Protein engineering Proteins). 

The calcium salt of the principal product, d/-tartaric acid, crystallizes with four molecules of water, while the secondary product, meso-tartaric acid, forms a calcium salt which crystallizes with three molecules of water. The amount of sulfuric acid actually required may readily be calculated from the percentage of calcium found on analysis in the regular way or it may be estimated by igniting a sample, and titrating the residue with standard acid. 

The residue of crystalline putrescine dihydrochloride is rinsed onto a Buchner funnel with the aid of 100-200 ml. of absolute ethanol used in several portions. The last portions of ethanol are used as wash liquid for the crystals. The crystals are finally pressed dry and washed with 25 ml. of ether. The air-dried product weighs 53-55 g. (72-74%) and melts above 275. Analysis for chlorine indicates that the salt is anhydrous. Concentration of the filtrate to a volume of about 25 ml. yields an additional 1-2 g. total yield 73-77%. The entire synthesis may be completed in one day. 

Other preparations and isolations. If damp methylenedi(nitroformamide) is allowed to stand for several days, the odor of formic acid is noticed, and MEDINA can be isolated from the residue (Ref 11, p 14). The details of scale-up to 150 lb batches, including exp details and flow sheets, and further scale-up with the aim of prodn of 1000 lbs are given. The report describes a fume-off and fire which occurred during the S3rd run. The cause was attributed to a stuck valve which allowed nitric acid to build up in the reactor (Ref 13, p 57). In Ref 16, p 73 there are cost analysis data for pilot plant and large scale prodn, flow sheet for a proposed coml plant, and material balances. The action of acet anhydr on N,Nf-bis(hydroxy-methyl)MEDlNA regenerates MEDINA (Ref 6) the diNa salt of N. N trinitrotrimethylene-diamine, on warming with me ale, ppts the Na salt of MEDINA... 

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