Abstract
PROF. G. G. HENDERSON, in delivering the twenty-sixth Bedson Lecture in Newcastle-upon-Tyne on May 18, outlined the work carried out in his laboratories on the subjects of gutta percha, balata and caoutchouc. The peculiar difficulties of the subject—which he advised research workers to avoid—are the lack of criteria of purity, complete absence of crystalline compounds, ready resinification at temperatures above 40°, and attack by air. Oxidation experiments with hydrogen peroxide yielded alcoholic substances in each case, which when treated successively with acetic anhydride, further peroxide and aqueous barium hydroxide gave, from each source, so far as could be determined, the same final alcoholic product. Hydrogenation with a palladium catalyst gave results in agreement with the general formulae (C5H8)x→ (C5H10)xa; with the anticipated increase in stability. This is in agreement with the general conception of chains of isoprene units linked head to tail with loss of one double bond per unit. The hydrochlorides of these substances on treatment with metallic zinc gave, not the same dihydrides, but quite different substances with the original empirical formula but one unsaturated linkage to each two isoprene units, which may be due to cyclisation on loss of hydrogen chloride. Finally, the dibromo addition compounds condensed with phenols in the presence of anhydrous ferric chloride to yield coloured substances with the properties of indicators, one being very suitable for the titration of halides with silver nitrate.
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Gutta Percha, Balata and Caoutchouc. Nature 133, 866 (1934). https://doi.org/10.1038/133866a0
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DOI: https://doi.org/10.1038/133866a0