Simple iron gall inks composed of gallic acid, ferrous sulfate, and gum arabic and in some cases also of copper(II) sulfate were prepared. The process of iron ion complex formation with gallic acid was investigated using UV-VIS spectroscopy, pH measurements, and by monitoring the concentration changes of Fe(II) ions. The admixture of Fe(II) ions to gallic acid induced a bathochromic shift of absorption bands at 215 nm and 265 nm in the UV-VIS spectra. Formation of a new absorbance band in the visible area was also observed and used to calculate the initial rate of complex formation. Concurrently, the pH values and the concentration of Fe(II) ions in the solution decreased. Gum arabic significantly enhanced the complex formation and its stability. On the contrary, the addition of Cu(II) ions to the solution decelerated the complex formation considerably.

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This article describes properties of composites of collagen-hyaluronic acid shaped to layered materials. According to the results, interactions of these two polymers are very strong. The properties can be influenced by chemical crosslinking using glyoxal and starch dialdehyde. The different behavior during enzymatic degradation by collagenase and in swelling experiments is discussed in relation to material composition. The valuable properties of the composites observed in this study show the possibility of their use as biomaterials.

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