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 (δ H ) of the acidic proton in the systems HCl/H 2 O and HCl/H 2 O/HOAc was correlated with the acidity function (H o ) 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 (H o ) I correlates with δ H in a way which can be rationalized. Addition of 7,5% (W) formaldehyde to these systems changes (H o ) I and δ H very significantly, particularly in systems with low water content. Logarithmic rate constants of cellulose formal formation in HCl/H 2 O/HOAc systems which do not show a linear relationship with (H o ) I , measured without presence of formaldehyde, do so if (H o ) I is measured with formaldehyde present. For these systems, however, δ H is not a suitable acidity parameter.