Acid concentration analysis

Aldehydes, enals, dienals, ketones, and hydrocarbons, which are responsible for disagreeable odors, generally bok at lower temperatures than fatty acids. Analysis showkig a free fatty acid concentration of less than 0.05% is an kidication that deodorization is sufficientiy complete. Some of the dienals have very low odor thresholds and sensory evaluation of the finished ok is a judicious quaHty assurance step. 

Descriptions of sulfuric acid analytical procedures not specified by ASTM are available (32,152). Federal specifications also describe the requited method of analysis. Concentrations of 78 wt % and 93 wt % H2SO4 are commonly measured indirectly by determining specific gravity. Higher acid concentrations are normally determined by titration with a base, or by sonic velocity or other physical property for plant control. Sonic velocity has been found to be quite accurate for strength analysis of both filming and nonfuming acid. 

Note The result of the analysis is extremely dependent on the acid concentration employed, the immersion time and the subsequent temperature and duration of heating. 

FIGURE 5.5 (a) The hydroxy amino acids serine and threonine are slowly destroyed during the course of protein hydrolysis for amino acid composition analysis. Extrapolation of the data back to time zero allows an accurate estimation of the amonnt of these amino acids originally present in the protein sample, (b) Peptide bonds involving hydrophobic amino acid residues snch as valine and isolencine resist hydrolysis by HCl. With time, these amino acids are released and their free concentrations approach a limiting value that can be approximated with reliability. 

Aqueous ceric solutions are widely used as oxidants in quantitative analysis they can be prepared by the oxidation of Ce ( cerous ) solutions with strong oxidizing agents such as peroxodisulfate, S20g ", or bismuthate, BiOg". Complexation and hydrolysis combine to render (Ce" +/Ce +) markedly dependent on anion and acid concentration. In relatively strong perchloric acid the aquo ion is present but in other acids coordination of the anion is likely. Also, if the pH is increased, hydrolysis to... 

The kinetic dependence of the reaction was explained in terms of a reaction between PhB(OH)3 and PhHg+. From analysis of the concentration of the species likely to be present in solution it was shown that reaction between these ions would yield an inverse dependence of rate upon molecular acid composition in buffer solutions, as observed for a tenfold change in molecular acid concentration, and that at high pH this dependence should disappear as found in carbonate buffers of pH 10. The form of the transition state could not be determined from the available data, and it would be useful to have kinetic parameters which might help to decide upon the likelihood of the 4-centre transition state, which was one suggested possibility. 

Satisfactory 40% peracetic acid is obtainable from Buffalo Electrochemical Corporation, Food Machinery and Chemical Corporation, Buffalo, New York. The specifications given by the manufacturer for its composition are peracetic acid, 40% hydrogen peroxide, 5% acetic acid, 39% sulfuric acid, 1% water, 15%. Its density is 1.15 g./ml. The peracetic acid concentration should be determined by titration. A method for the analysis of peracid solutions is based on the use of ceric sulfate as a titrant for the hydrogen peroxide present, followed by an iodometric determination of the peracid present.3 The checkers found that peracetic acid of a lower concentration (27.5%) may also be used without a decrease in yield. The product was found to be sufficiently pure, after only one recrystallization from 60 ml. of petroleum ether (b.p. 40-60°) and cooling overnight to —18°, to be used in the next step. 

Since it is possible to differentiate well-preserved from badly preserved collagen through amino acid analysis and gel electrophoresis, it is also possible to determine which bone samples are likely to give erroneous isotopic ratios. At least for 8 C, it should be possible to estimate the in vivo isotopic signature by correcting the changed amino acid concentrations of the collagen extract. This way, a reasonable approach to the reconstruction of pale-odiet should be possible. 

The same procedure, or modifications of it, was used by Zak et al (80), Talseth (42,82,82,83), and Haegele et al (46) for metabolic studies. Zak et al (80) point out that hydrolysis of conjugates of the drug may cause analytical results on biological samples to be variable, depending on the acid concentration during derivatization, and that selective analysis for unchanged hydralazine and acid-labile metabolites can be carried out by suitable adjustment of the acid concentration. 

The EDX spectrum (Fig. 11.8) shows the main surface scale impurity peaks of silica, aluminium, sodium, chloride and iron. If this EDX is compared to that of a new, clean membrane surface (Fig. 11.9), the clean surface shows sulphur, carbon and oxygen, which is typical of a porous polysulphone support. It was concluded that the scale is amorphous, composed of aluminosilicate and silicate. These compounds are normally found in trace amounts in brine solutions. Analysis showed that the surface could be cleaned with hydrochloric acid and analysis of the dissolved scale was similar to the EDX spectrum analysis. Review of the plant operation determined that the precipitation was the result of high pH in combination with high silica concentrations in the brine. 

FIGURE 3.24 Dendrogram of fatty acid concentration data from mummies and reference samples. Hierarchical cluster analysis (complete linkage) with Euclidean distances has been applied. 

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