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Published online by Cambridge University Press: 06 July 2012
The first step made in this investigation was the recognition of increased specific electrical conductivity as a general characteristic of photochemical action. It was argued that if there be any common characteristic in photochemical changes it must be found in the simplest as well as in the more familiar and more complex reactions which are characteristic of the metabolism of plants.
No chemically simpler case suggested itself than the increase in electric conductivity of crystalline selenium under the influence of light. This change might indeed be held almost to lie outside the range of chemistry proper, and to belong to the class of change often spoken of as merely physical change. But no sharp line can be drawn between physical and chemical changes, and the clue proved most useful.
page 117 note * On Photochemical Action, Proc. Roy. Soc. Edin., 1897, vol. xxi. p. 303Google Scholar.
page 117 note † Comp. Zeit. physik. Chemie, lxvi. p. 58Google Scholar.
page 118 note * This is clearly recognised by Meyer, loc. cit.
page 118 note † Gibson, J., Trans. Roy. Soc. Edin., 1905–1906, vol. xli. p. 241Google Scholar.
page 120 note * Gibson, and Denison, , Proc. Roy. Soc. Edin., vol. xxx. p. 562, 1909–1910Google Scholar.
page 121 note * Comp. Backelandt, , Bull, de l'Académie royale de Belgique, 3me série, t. xl., Nr 3, 1886Google Scholar.
page 125 note * The term “polymerisation” is here intended to include cases of condensation of the aldol type which are not accompanied by a permanent hydrolysis or dehydration.
page 126 note * According to conductivity determinations made in this laboratory.
page 133 note * Brown, and Morris, , “The Chemistry and Physiology of Foliage Leaves,” Chem. Soc. Jour., 1893, p. 637Google Scholar.
page 135 note * This statement requires modification in one case only, viz. so far as mustard and saturated solution of potassium iodide are concerned, for this solution has a marked disintegrative effect and appears to produce a deepergoing change which masks the tendency of the premaximal system.
page 136 note * Proc. Roy. Soc., 1909, vol. lxxxi. p. 82Google Scholar.
page 136 note † See page 124 et seq.