In light Kundt's name is widely known for his inquiries in anomalous dispersion, not only in liquids and vapours, but even in metals, which he obtained in very thin films by means of a laborious process of electrolytic deposition upon platinized glass.
Dennstedt, which was first proposed in 1902, the substance is vaporized in a tube containing at one end platinum foil, platinized quartz, or platinized asbestos.
The residual gas is then passed through a tube containing porous materials, such as woodor bone-charcoal, platinized pumice or spongy platinum, then mixed with steam and again forced through the tube.
Platinized platinum (platinum foil upon which a thin film of platinum had been deposited electrolytically) and charcoal were rendered incandescent, black paper and matches immediately inflamed, ordinary brown paper pierced and burned, while thin white blotting-paper, owing to its transparency to the invisible rays, was scarcely tinged.
It may be prepared by distilling fuming sulphuric acid, or concentrated sulphuric acid over phosphorus pentoxide, or by the direct union of sulphur dioxide with oxygen in the presence of a catalyst, such as platinized asbestos (see Sulphuric Acid).