Physical Society's Duddell Medal : Dr. E. H. Land


    THE Duddell Medal for 1949 of the Physical Society was presented on June 2 to Dr. Edwin Herbert Land, inventor of the polarzing material 'Polaroid'. Though attempts had been made by previous workers to replace the costly and limited Nicol prism with dichroic substances in the form of thin laminæ, Land was the first to demonstrate the possibility of manu-facturmg such laminæ with sub-microscopic dichroic crystals of quinine iodosulphate correctly oriented to late a single crystal extended to a superficial area previously considered impossible. This method is now being superseded as the result of two stages of further development. In the first, a plastic medium is stretched to cause orientation of the micelles. It is then soaked in a solution of the iodonium compound, which is precipitated on the oriented micelles to produce a polarizing medium. In the final method, a stretched plastic medium is treated in a way which converts about 1 per cent of its bulk to a polyvinylene compound, a straight-chain polymer in which the double-bonded oxygen gives the necessary intense directional light absorption. It is claimed that this material is extremely heat-stable and very efficient. The light transmission of the single sheet is about 40 per cent, and is reduced to 0·02 per cent for two sheets in the crossed position. This is a very remarkable development of the original idea. First, Land has succeeded in eliminating the step of orienting sub-microscopic crystals of the iodonium compound ; secondly, he has eliminated the compound altogether.

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    Physical Society's Duddell Medal : Dr. E. H. Land. Nature 163, 866 (1949).

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