VI. Some experiments and observations on a new substance which becomes a violet coloured gas by heat

A new and a very curious substance has recently occupied the attention of chemists at Paris. This substance was accidentally discovered about two years ago by M. Courtois, a manufacturer of saltpetre at Paris. In his processes for procuring soda from the ashes of sea weeds, (cendres de vareck) he found the metallic vessels much corroded; and in searching for the cause of this effect, he made the discovery. The substance is procured from the ashes, after the extraction of the carbonate of soda, with great facility, and merely by the action of sulphuric acid:— when the acid is concentrated, so as to produce much heat, the substance appears as a vapour of a beautiful violet colour, which condenses in crystals having the colour and the lustre of plumbago.