Acids Of Different Strengths Research Articles

Voltammetric determination of the titrable acidity of milk using a platinum microelectrode

AbstractA platinum microelectrode with a radius of 12.5 μm was employed for determining the acidity of crude bovine milk samples by voltammetric titration. Solutions of sodium hydroxide and of several acids of different strengths were used as titrants. The relative standard deviation (RSD) was within 3%, regardless of the type of titrant agent employed. The data found with this approach were compared with those obtained by the classical methods commonly employed for the determination of the titrable acidity of milk.

An alternative procedure for titration curves of a mixture of acids of different strengths

An alternative procedure is presented that allows us to get the same kind of information using a single equation plus a graph, that would normally be determined by two plots.

An assessment of methanolysis and other factors used in the analysis of carbohydrate-containing materials.

The stability of monosaccharides in methanolic hydrochloric acid of different strengths and at different temperatures was determined. They are generally stable for 24h in methanolic 1m- and 2m-hydrochloric acid at both 85 degrees C and 100 degrees C, but undergo considerable destruction in methanolic 4m- and 6m-hydrochloric acid at 100 degrees C. Analysis of glycopeptides and oligosaccharides of known composition showed that release of carbohydrate was complete within 3h in methanolic 1m-hydrochloric acid at 85 degrees C. Removal of methanolic hydrochloric acid by rotary evaporation resulted in considerable losses of monosaccharides, which could be prevented by prior neutralization. Methanolysis caused extensive de-N-acetylation of acetamidohexoses, so that a re-N-acetylation step is necessary in the analytical procedure. The addition of acetic anhydride for this purpose also prevented loss of internal standard by adsorption on the insoluble silver salts used in neutralization. Several trimethylsilylating agents were studied and suitable conditions are recommended. The effects on the analytical system of water and some common organic and inorganic contaminants are assessed.

Investigations on polyesterification reactions

The authors' previous assumptions for the effect of the first and second dissociation constants of a dicarboxylic acid on its polyesterification reactions with diols have been justified by model tests. In addition, the concept of polyesterification as a proton catalytic reaction has been confirmed. The studies included the following experiments: Diesterifications of dicarboxylic acids of different strengths and their monoesters with methanol; equilibrium esterifications of dicarboxylic acids of different strengths with diols; following the consumption of free glycol during the polyesterification.

MOLECULAR SIEVE SORBENTS FROM CLINOPTILOLITE

Clinoptilolite has been investigated as a source of porous, largely crystalline, molecular sieve sorbents. By treating the zeolite with mineral acid of different strengths a range of high area sorbents has been produced, in which all the original cations have been replaced by hydronium ions, and in which the aluminum has been progressively removed from the frameworks. The new sorbents and the original clinoptilolite have been characterized by sorption studies, and by X-ray, electron optical, differential thermal analysis, and thermogravimetric methods. The most open molecular sieve sorbents, able to imbibe considerable amounts of larger molecules such as benzene and isopentane, were obtained using 1 N and 2 N acid, but as acid strength increased further there was a decline in both crystallinity and sorption capacity until with 30 N acid an amorphous product resulted.

The separation of the rare earths by partition chromatography with reversed phases : Part II. Behaviour of individual elements on HDEHP-CORVIC columns

The elements lanthanium, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium have been eluted by perchloric and hydrochloric acid of different strengths from columns of di-(2-ethylhexyl) orthophosphoric acid retained on poly-(vinyl chloride/vinyl acetate) copolymer. From these results separation factors have been calculated and these are compared with values obtained from solvent extraction determinations with the alkyl-phosphoric acid dissolved in toluene.

CXXVIII.—The estimation of nitrites by means of thiocarbamide, and the interaction of nitrous acid and thiocarbamide in the presence of acids of different strength

CXXVIII.—The estimation of nitrites by means of thiocarbamide, and the interaction of nitrous acid and thiocarbamide in the presence of acids of different strength

Societies and Academies

Societies and Academies