Recent Foreign Inventions and Discoveries: Naphthaline Purple Dye.

Scientific American. / New Series 19, 10.5.1862

- W. L. Scott, of Bayswater, England, has obtained a patent for a product of binitro-naphthaline as the basis for red and other dyes. He takes ten parts of sulphuric acid (specific gravity 1.650) and heats it to 360° Fah., and adds to this from two to four parts of binitro-naphthaline, and a small quantity of sulpho-naphthalic acid. When the mixture is completed small strips of zinc are added for the purpose of deoxidizing it, and when it is fully deoxidized the color becomes deep red. It is now allowed to cool, some dilute alkali, such as soda, added partly to neutralize the free acid, and the whole is then boiled for a short period of time under pressure. The liquor is now filtered, and the clear coloring matter separated from the precipitate. By treating the precipitate with benzole, or an alkali, all the red matter is extracted. It is called dianthine. When this product is treated with nitric acid so as to form the nitrate of dianthine, and this again treated with ammonia and alcohol, it makes a beautiful red dye of a scarlet tint.