Abstract
LONDON. Royal Society, March 18.—Sir Archibald Geikie, K.C.B., president, in the chair.—An attempt to detect some electro-optical effects: Prof. H. A. Wilson. The paper contains a description of some experiments made with the object of detecting possible effects due to electric and magnetic fields and moving matter on the velocity of propagation of light in glass. The results obtained were negative, but it seems worth while to publish a short account of the experiments. The optical part of the apparatus is a simple form of interferometer, which proved very easy and convenient to work with. It consists of a square glass frame made up of glass bars of square cross-section, cemented together with Canada balsam.—The influence of their state in solution on the absorption spectra of dissolved dyes: Dr. S. E. Sheppard. In the aqueous solutions of certain dyestuffs—isocyanines, pinacyanols, cyanine—the dye is present partially or wholly in colloid solution, and the absorption spectrum is quite different from that of the true solution. The influence of various agencies, as heat, acid and alkali, electrolytes on the absorption was examined quantitatively. In other dye solutions the change from true solution to the colloid state is accompanied by broadening and diffusion of the absorption curve, consequent on the increase in number and size of the colloid particles. Deviations from Beer's law result. The state of dyes in solid media is comparable with that in liquid, and the absorption spectrum is similarly affected. The absorption of a number of dyes by membranes was studied. The solution of dyes appears to be a combined process of disaggregation of the solute, accompanied by a progressive combination with the solvent. If the same stage of solution is attained in different solvents, the absorption maxima are displaced according to Kundt's law.—The ferments and latent life of resting seeds: Jean White. The resting seeds of cereals such as wheat, maize, barley, oats, and rye all contain diastatic, fibrin-digesting, and ereptic ferments in appreciable amount. These ferments retain their activity without appreciable change in stored dry seeds for twenty or more years, that is, long after the power of germination has been lost, which takes place in wheat after eleven to sixteen years, barley eight to ten years, oats five to nine years, maize and rye more than five years. No relation was noted between the vitality of seeds and the persistence of enzymes in them, but since the enzymes persisted longer than the power of germination, the question as to whether germination could take place in the absence of any pre-existent enzymes remains to be answered. In any case no otherwise non-germinable seeds could be excited to germination by the addition of any kind of enzyme, and where the germination was feeble the addition of enzymes usually lowered the percentage germination and often delayed germination also to some extent. The erepsin appears to be more abundant than the pepsin, but otherwise in the cases of all three ferments greater differences are shown between different samples of the same age than between different seeds, or between the same seeds of varying ages. Pepsin appears, however, to be more abundant in rye than in any other cereal, and is almost absent from maize. Dry oats, barley, and wheat can in part resist a temperature of 99° C. to 100° C. for 1–4½ hours; after six hours' exposure all are killed, but the ferments are apparently unaffected. All the ferments are destroyed after an hour's dry heat at 130° C. to 131° C. The pepsin appeared to be least (one hour at 124° C.), the erepsin more (one hour at 124° C. to 128° C.), and the diastase, especially of barley, most resistant to dry heat (one hour at 124° C. to 131° C.). Two days' exposure to liquid air, although it delays the subsequent germination, and may also decfease the percentage, did not absolutely destroy any of the seeds tested, and did not appreciably affect the ferments in any of the cereals. The dry diastase of barley is therefore able to withstand a range of temperature of 200° C. to —130° C.; it is therefore thermally a highly stable chemical compound. Many seeds, including all cereals, give off appreciable quantities of carbon dioxide when stored in the air-dried condition, but others show no signs of respiration whatever. The respiration of air-dried wheat is especially pronounced, but in practically all cases every sign of respiration ceases when the seeds are moderately desiccated, although in the case of large seeds like maize minute traces of carbon dioxide may continue to escape for a time.
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Societies and Academies . Nature 80, 118–120 (1909). https://doi.org/10.1038/080118a0
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DOI: https://doi.org/10.1038/080118a0