Scientific American 17, 27.4.1861
The following are condensed descriptions of several patents lately taken out in England, connected with the chemical art of manufacturing and applying colors: -
Purples from Coal tar Products. - R. Smith, a well known chemist, has obtained beautiful colors, not only from aniline, but other bases found in coal tar. He takes a saturated solution of aniline, toluidine, xylidine, cumidine, or either of them in water, and adds a solution of chlorine in water. The proportions are from 1 to 3 equivalents of chlorine to one equivalent of the bases. The mixture is allowed to stand for twelve hours, when a black percipitate is found at the bottom of the vessel. This is washed with water, then mixed with a solution containing about five per cent of soda. In about two hours the solution is filtered. The precipitate is now boiled until the coloring matter is dissolved, when it is filtered, and a small wuantity of the chloride of calcium added. This separated the coloring substance, which is collected in a filter, and washed well with cold water. The coloring matter is now dried, and may be afterward dissolved in alcohol, or wood spirit, and is then ready for dyeing or printing. The color so obtained is a bright purple, similar to that called mauve, which is obtained from aniline by mixing it with manganates, or the bichromate of potash.
Coloring and Gilding Leather and other Fabrics. - A patent has been secured by R. A. Brooman (being a communication from abroad) for an improvement in printing in relief, and in color, and in gold or silver. The material or fabric to be ornamented or colored is passed between a pair of rollers, one of which is metal, and has the desired pattern sunk or cut out on it, while the other roller is the counterpart, and is formed of gutta-percha or hard paper, wit the pattern in relief. For printing with one color only, a distributing roller is placed in contact with the relief roller, and as it revolves, the color is supplied to its surface. For printing in several colors, the inventor uses what he terms "cliche" rollers of gutta-percha, which have their surfaces in relief. The fabric is passed through in a piece as in calico printing, and the pattern is printed in color, and embossed at one continuous operation. When portions of the pattern are to be gilded, the rollers print sizes or mucilage on the parts, and when the fabric passes through, the gilding is applied in powder dusted upon it. This adheres to the prepared surface, and when dried it may be run between pressure rollers to smooth it down.
Panphiteic Acid - New Color Agent. - H. Johnson has obtained a patent (communicated from abroad) of a peculiar new coloring matter obtained from several plants and vegetables. When vegetables are treated with steam, or boiling alkaline water, a coloring substance is extracted from them, and precipitated. This is placed in a stoneware vessel, mixed with nitric acid, and evaporated. The residuum thus obtained contains panphiteic acid, and it is now placed in distilled water, and washed. Resins, gums, wax, and all vegetable exudations may be converted into panthiteic acid, by first dissolving them in alcohol, ammonia, or bisulphuret of carbon, then submitting such solutions to the action of strong nitric acid; or the wax, &c., may be first treated with nitric acid, and secondly, with the alcohol or other solvent. Panphiteic acid produces a yellow dye, and by mixing it with the prussiate of potash, it imparts a light green color to silks and woolens, by simply dipping them into a solution of it. Panphiteic acid, obtained from catechue, can be employed for dyeing shades of dark green on cotton, by preparing the fabric first in a bath containing a solution of nitrate of iron.
Purple-blue Color. - Mr. Johnson has also obtained a patent for a new purple-blue color, derived from indigo, and designed for dyeing and printing on textile fabrics. Take, say 20 lbs., of anhydrous bisulphate of soda, and heat it until it becomes fused. In this condition, about one pound of pulverized indigo is added to it gradually, and the mixture constantly stirred to prevent it from sticking to the bottom of the vessel, which may be a cast iron kettle. The mass now swells, and becomes very dark in color, and disengages a great deal of gas. By taking a little of it out occasionally upon a glass rod, and stirring it among some clear water in a glass tumbler, the progress of the operation is tested; as soon as it colors the water a violet red, no more indigo should be added. The mixture should now be of a pasty consistency. About 147 gallons of hot water are then placed in a cask, and the mixture poured into it and actively stirred; this precipitates the coloring matter, which is a beautiful purple-blue, of a peculiar and brilliant color.
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