The Polytechnic Association of The American Institute.

Scientific American 15, 6.10.1860

(Reported expecially for the Scientific American.)

The usual weekly meeting of this association was hels at the Institute rooms, on Thursday evening, 26th inst; Professor C. Mason presiding.

Miscellaneous Business.

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Aniline and Coal Oil. - Dr. Stevens exhibited about two dozen samples of silks and delaines dyed with the above compounds. The colors are of various tints of red, purple and lilac. The Doctor remarked that aniline, the base of all these colors, is one of the products of the distillation of coal, and may always be found in coal tar and crude coal oils. The great value of these dyes, beyond their brilliancy, is the fact that they are permanent, a quality which was long sought for in vain. The famous Tyrian purple frota the shellfish murex was considered a fast color, but its cost and its limited supply have kept it out of use in modern times.

Mr. Seely - Aniline and its compounds which are used as dues have been known for a long time among chemists, but were regarded only as substances of scientific interest; their utility as dyes, however, is a discovery which has been developed within a year or two. Coal tar and crude coal oil are made up of about forty different compounds, acids, alkalies or bases and neutral substances. Amond the acids is creosote; the alkalies, ammonia, and the neutral substances, coal oils. Aniline is one of the alkaline substances, and, according to the French chemists, in its chemical character is similar to ammonia. It unites with acids and forms salts, and it is solutions of these in alcohol which are the dyes. Thus, the mauve dye is a chromate of aniline, and the solferino is similar in its constitution to ammonia-sulphate of copper. In coal tar the aniline is in such a small quantity that it is impracticable to separate it unless at the same time, the coal tar is treated for other more important purposes. It is, however, obtained in abundance from benzole, which is the lightest of the coal oils, by a chemical process which is not difficult for a skillful chemist. The new colors are extremely popular with the ladies, and all the dyers will, no doubt, be anxious to learn the new improvement in their art.

The President - Wherein consists the peculiar virtue of coal over other oils?

Mr. Seely - I think it lies mainly in the fact that they are neutral substances. They have no affinity for oxygen at ordinary temperatures, and they will not become resinous or rancid; they are almost as unchangeable as water.

Dr. Stevens - I have found the practical difference to be that if "you spill coal oil on a carpet, no harm is done; while if it be fish oil, an indellible stain is left."

[Laughter.]

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