Manganese-bismuth film

The information is read out by a second laser beam deflected onto the hologram of the manganese-bismuth film but not onto the liquid crystals. Erasure is similar to writing except that neither of the beams is modulated or coded by the liquid crystals. The point on which the two laser beams meet is therefore magnetically neutralized. The film suffers no damage, and the write, read and erase processes can be repeated at will. 

Other metals, the commonest being lead,2 bismuth, and manganese, in powder form exert a more moderate effect on the decomposition. Mercury would also fall into this class of moderate accelerators, but the catalytic action in this case is remarkable in being periodic or rhythmic. When the concentration of hydrogen ion is reduced to an almost negligible quantity by the addition of a little sodium acetate solution, a clean mercury surface in contact with hydrogen peroxide solution of approximately 10 per cent, concentration, at periodic intervals of about one second, becomes coated with a bronze film which suddenly disappears with a burst of oxygen from the contact layer of the two liquids the substance of the film, which is alternately formed and decomposed, is probably an unstable oxide, possibly mercurous peroxide.3... 

The so-called mechanical passivity, accompanied by the formation of a visible film and oxygen evolution, has been observed with iron, cobalt, nickel, manganese, lead and other anodes in alkali hydroxide solutions, and also with thallium, antimony and bismuth in aqueous sulfuric acid. 

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