Abstract
LONDON. Royal Microscopical Society, April 16.—Mr. J. E. Barnard, president, in the chair.—J. Strachan: The chemistry of dendritic growths in paper. The formation of these interesting and curious growths was formerly attributed to the oxidation of a particle of bronze or brass included in the sheet of paper during manufacture. Later investigations have proved, however, that the chemical reactions producing these growths are more complex. The particle of bronze is attacked by chemical residues in the paper, chief among which is sulphate of aluminium, with the formation of soluble sulphate of copper. The latter creeps along the fibres in solution. The sulphate of copper is then reduced to insoluble black sulphide oof copper, which constitutes the majority of recent dendrites in paper. This sulphide is further oxidised again to sulphate, and so by alternate oxidation and reduction insoluble copper compounds may be deposited along the fibres. The final action in old dendrites is oxidation, resulting in the formation of basic copper sulphate. The chemistry of these growths is important in that they indicate, by secondary reactions, the nature of chemical actions taking place in the deterioration of paper during ageing, in which the cellulose is attacked by chemical residues from various sources. A new rnicro-chemical test for the detection of copper sulphide consists in the application to the dendrite of a solution containing the double cyanide of potassium and cadmium. The black copper sulphide dissolves, but is exactly replaced by a brilliant yellow pseudomprph of cadmium sulphide, forming a yellow dendrite. The principle of this mode of testing, by replacement appears to be capable of further applications in micro-chemical manipulation.—Dr. E. Penard: Folliculina boltoni, S. Kent. In spite of recent statements to the contrary, the genus Folliculina is undoubtedly represented in fresh-water, and the vermiform bodies (described-as Lagynus ocellatus, by Daday) represent, as already suspected by several authors, though contradicted by others, a free-swimming form produced by a metamorphosis of the whole individual.
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Societies and Academies . Nature 103, 219 (1919). https://doi.org/10.1038/103219a0
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DOI: https://doi.org/10.1038/103219a0