Naphthaline Colors

Scientific American 11, 15.3.1862

The following is the substance of recent remarks by the celebrated French chemist J. Persoz before the Academy of Sciences, Paris. He said: -

Starting from the fact established by us, that a mixture of commercial nitric and sulphuric acids, even in very variable proportions, will, when heated with naphthaline, readily yield colored products, we have naturally been led to examine the action of concentrated sulphuric acid on the various nitrogenized compounds of naphthaline.

This is a very diffucult study, however simple it may at first appear, because the least changes of the condition under which the experiment is performed, exercise a sensible influence on the results. The dye principle formed, possesses the property of madder in dyeing with mordants; its color varies from red to blue and passes through all the shades of violet.

The blue was only obtained accidentally; and we are unable to state the precise conditions of its formation, though it appears to be due to molecular change in the nitrogenized naphthaline compound, under the influence of a physical agent.

As the violet-blue tints are the most beautiful, we have devoted most of our attention to them, and have endeavoured to produce them. We soon found that binitronaphthaline, heated, with sulphuric acid only, was best suited to our purpose. In his last communication to the Institute M. Roussin says: -" By making concentrated sulphuric acid reaction on binitronaphthaline, no reaction takes place. The binitronaphthaline is completely dissolved when the mixture is heated to 250°, and the liquid taked hardly an amber color. After boiling for a long time, the concentrated sulphuric acid began to react on this substance." Binitronaphthaline resists the action of sulphuric acid at  a very hight temperature, however, at about 300° ; the color of the solution, at first slightly yellow, deepens more and more, becomes cherry-red, beginning, at the same time, to disengage a small quantity of sulphurous acid.

The substance is then taken from the fire, and left to cool when it is poured into a proper quantity of water and boiled. The liquid, filtered whilst hot, is of a deep red color, and deposits part of the coloring matter in a flaky state. Alkalies change it to violet red; and even when cold, silk was easily dyed violet by it. After being properly saturated with the alkalies, and finally with a little chalk, it dyed mordanted cotton tissues with different shades, varying from lilac to black. The lake alum, tin, and lead for a base, are violet; those with iron for a base, were olive, and sometimes reached to black.

This solution does not seem to alter even during any length of time, in presence of sulphuric acid; though, when in contact with air ad excess of ammonia, it changes to brown in a few hours, depositing a black powder, which becomes blue dissolved in alcohol, and red in acids.

The black mass proceeding from the precipitation of the sulphuric solution by water, contains a large quantity of coloring matter, has a beautiful gold reflection, is very soluble in alcohol and pyroligneous acid; but very little soluble in water, ether, benzole, and bisulphide of carbon. It has many chemical analogies with alizarine. The dyed tissues bear brightening with soap.

With binitronaphthaline and concentrated sulphuric acid only, without making use of a reducing agent, a coloring matter may be obtained with marked analogies to alizarine in its chemical properties.