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Wechsberg, H. E. (1955) A study of zinc complex compounds with reference to rubber (hevea) latex. Doctoral thesis, Northern Polytechnic.
The destabilisation of natural rubber (Hevea) latex by zinc oxide constitutes an important technological problem in which the formation of complexes between zinc and certain non-rubber serum constituents is known to play a critical part. This complex formation has been examined (with particular reference to conditions at high pH and high ligand concentration) by means of solubility, polarographic and potentiometric methods, the ligands being (i) ammonia (ii) simple carboxylic acids, (iii) monocarboxylic amino acids, (iv) dicarboxylic amino acids, (v) glycerophosphoric acid, (vi) quebrachitol and (vii) pentachlorophenol. The nature and the stability constants of the complexes formed with ligands (i) - (iv) have been determined. No significant interaction between zinc and (v), (vi) and (vii) could be detected. Contrary to some previous evidence, which is critically discussed, the effect of carboxylic acid anions on complex formation in ammonia has been shown to be negligible. To assist in the interpretation of some of the experimental data, a new method of calculating stability constants has been developed. The method is applicable both to formation curves and to various types of central ion data, and is discussed in relation to existing calculation procedures; its use is demonstrated by a series of examples taken from the literature and by the data obtained in the present investigation. Other work, ancillary to the main investigation, includes determinations of the various ligand dissociation constants and improvements in a) the preparation of crystalline zinc hydroxide and b) the design of a cell for accurate pH measurements.
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