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Acidities of Hydrochloric Acid in Water/Acetic Acid and in Water/Acetic Acid/Formaldehyde Mixtures: Investigations with the indicator method and with the nmr method. 31st communication on investigations in textile chemistry
The NMR. chemical shift (δH) of the acidic proton in the systems HCl/H2O and HCl/H2O/HOAc was correlated with the acidity function (Ho)I determined by the indicator method. By using three indicators it could be shown that, except for solutions with very low concentrations of hydrochloric acid, the acidity function (Ho)I correlates with δH in a way which can be rationalized. Addition of 7,5% (W) formaldehyde to these systems changes (Ho)I and δH very significantly, particularly in systems with low water content. Logarithmic rate constants of cellulose formal formation in HCl/H2O/HOAc systems which do not show a linear relationship with (Ho)I, measured without presence of formaldehyde, do so if (Ho)I is measured with formaldehyde present. For these systems, however, δH is not a suitable acidity parameter.