FINAL ANALYSIS

First paragraph: Platinum (as well as many other metals) may\udbe prepared in finely divided forms that are\udporous at all levels of magnification. Cracks and\udcrevices in the sponge-like opaque matrix then\udallow visible light (of wavelength around 0.5 μm)\udto enter, whereupon it undergoes multiple reflections\udand is unlikely to be reflected back out. This\udeffectively produces a high value for optical\udabsorption, resulting in a velvety black appearance\udto the eye, even though the platinum is in\udthe metallic state. Other porous structures (such\udas snow and plaster) consist of inherently transparent\udor translucent crystals, so light can be\udrefracted as well as reflected out and they appear\udmatt white.Peer-reviewedPublisher Versio