Artificial Madder.

Scientific American 3, 20.7.1861

M. Dumas lately announced to the Academy of Sciences of Paris, hat M. Roussin had obtained alizarine (the coloring principle of madder) from naphthaline, as follows: -

A mixture of binitro-naphthaline with concentrated and pure sulphuric acid is placed in a large porcelain capsule heated by an oil or sand bath. By raising the remperature, the binitro-naphthaline dissolves completely in the sulphuric acid. When the micture has reached 392° Fah., granulated zinc is dropped into the mixture gradually, and with careful observation not to allow the temperature to rise much. In a few minutes a disengagement of sulphuric acid takes place, and the operation is terminated in about half an hour. If a drop of the acid liwuid is then allowed to fall into cold water, a magnificent violet color is developed, due to alizarine.

When the reaction is over, the liquid is diluted with eight or ten times its volume of water and brought to the boiling point, and after boiling a few minutes, thrown into a filter. The alizarine is deposited upon cooling as a red jelly; sometimes adhering to the vessels - sometimes suspended in the liquid. Examined by the microscope, it is seen to be composed of needle-shaped crystals of great definiteness. The mother waters are strongly red from dissolved alizarine, an may be used to dye directly. A quantity of alizarine remains in the filter, which may be removed by caustic alkalies.

In the preceding reaction, the zinc may be replaced by any one of a number of substances - such as iron, mercury, sulphur, carbon, or, in short, by any substance which reacts at a high temperature with sulphuric acid, with the production of sulphurous acid.

The substance thus obtained possesses all the characters and reactions of alizarine. It is but slightly soluble in water, but soluble in alcohol and ether; volatilizes between 419° and 464° Fah., with a yellow vapor, and gives deep red needle-shaped crystals, whose tone of color is very variable. It is not attacked by chlorhydric or concentrated sulphuric acid. It dissolves in caustic and carbonated alkalies, with a deep purple color. Acids precipitate this solution in deep orange-red flocculi. Like alizarine from madder, it furnishes lakes of the most beautiful colors. It is fixed on stuffs like natural alizarine, and gives similar tints.

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