Harper's New Monthly Magazine/Vol. XLIV/No. 261/February 1872/Editor's Scientific Record/Acridine, a New Anthracene Derivative
A basic substance has lately been separated by Graebe and Caro from crude anthracene, to which, on account of its irritating action upon the skin and mucous membranes, they have given the name of acridine. This body is obtained by heating the semi-solid portion of coal naphtha, which boils between 300º and 360º, with dilute sulphuric acid, and precipitating the acid solution with potassium dichromate. A dirty brown precipitate is obtained, which dissolves on repeated treatment with boiling water. The solution thus obtained yields, after filtration and cooling, orange-yellow crystals of the chromate of the base; these crystals, freed from the mother-liquor by washing, yield the free base when warmed with ammonia. Thus obtained the body is not quite pure; but it may be rendered so by recrystallizing its hydrochloride. Acridine substance crystallizes, as determined by Dr. P. Groth, in small, four-sided, rectangular prisms of the rhombic system, whose edges are often, but narrowly, truncated by the vertical prism, while the ends are formed by obtuse domes.
Acridine melts at 107º, and distills without alteration at a temperature above 360º. It sublimes, even below its melting-point, in large, broad needles. It is almost insoluble in cold, and but little soluble in boiling, water. On the other hand, it dissolves readily in alcohol, ether, carbon-bisulphide, and hydro-carbons. The dilute solutions show a beautiful blue color by reflected light. It exerts a slight but distinct alkaline reaction on litmus. When inhaled, either in dust or vapor, it causes sneezing, and in large quantity coughing. It is exceedingly stable, and may be distilled unaltered over either ignited zinc or soda-lime, although most readily attacked by sodium amalgam. Two series of salts of acridine have already been prepared by the authors, and numerous compounds with other substances examined by them.