Abstract
II. WE have hitherto treated the question of a sensitive compound from what may be called a chemist's point of view, but it has also its physical aspect, and to enable us to understand what has recently been done in photography this latter must be briefly touched upon. To commence with, we are met with a difficulty in nomenclature which ought not to exist. Unhappily chemists and physicists employ the term molecule in a different sense. The physicist's molecule, for instance, in one place is defined2 as “a small mass of matter the parts of which do not part company during the excursions which it makes when the body to which it belongs is hot.” To avoid misapprehension the expression molecular group will be used for the physicist's molecule for want of a better, the word particle being rather too indefinite, and being usually applied to a group of molecules of visible size, a state of aggregation which is by no means necessary. The question as to the possible variation of the number of molecules composing a molecular group has not been entered into, as it would be trenching on ground which has been explored by others in relation to a different subject; but this may be stated as a matter of observation that some compounds of silver which are sensitive to light are capable of forming two molecular groups, one of which absorbs the blue rays, and the other the red rays.
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References
Continued from p. 491.
Proc. Roy. Soc., vol. x. pp. 326–338
"Theory of Heat", Maxwell .
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ABNEY, W. PHYSICS IN PHOTOGRAPHY 1 . Nature 18, 528–531 (1878). https://doi.org/10.1038/018528a0
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DOI: https://doi.org/10.1038/018528a0