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HIGH-SCHIIOL CHEMISTRY
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Dyes and Dyeing for Beginners CHARLES H . STONE Vermont Junior College, Montpelier, Vermont OR the pupil who shows somewhat more than the rinse under the faucet, squeeze as dry as possible, and usual Interest in chemistry the teacher may pro- finish drying between sheets of blotting, and finally vide projects of different character according to the filter, paper. pupil's inclinations. Experiments with textiles may Fast Red is another easily prepared dye for wool. well prove of interest, for the results are always colorful. Dissolve 5 g. sodium naphthionate in 25 cc. water, add Fibers are classified in most textbooks, and tests for 2 g. sodium nitrite dissolved in a little water, stir, and identification of wool and cotton are given, such as: acidify slightly with dilute hydrochloric acid. Pour this solubility of wool in hot 5 per cent sodium hydroxide cold solution, with stirring, into a solution of BN solution, and the familiar reaction of cotton to sulfuric (4 g. dissolved in a minimum amount of sodium hyacid. The separation of wool from cotton may be ac- droxide solution); stir and let stand overnight. Then complished as a project, taking advantage of the effect proceed as above for Orange 11. of sulfuric acid. When the goods are dry the cotton To apply the dye, make a bath of 100 cc. water and may be dusted out, leaving an inferior grade of wool enough Fast Red to give a good color. It is surprising how little of the dye is required in any case to give the known as "shoddy." Textile dyes may be classified as acid, basic, sub- desired result. Do not make the mistake of using too stantive, vat colors, and various others. The equations much of the solid dyestuff. A fine red on wool results for the preparation of many dyes are quite complicated, when the skein is boiled in the bath. In any case the and no attempt should be made to teach such equations finished dry skein may be mounted on a colored card to beginners. Nevertheless, any student of average with samples of materials used contained in small test ability and with good interest in the subject can pre- tubes, and the story of the experiment written out in pare a number of dyes and apply them to the goods for detail. Such a project can hardly fail to interest the which the dye is suited. pupil. B i s m r k Brown is easily prepared. Dissolve 5 g. Orange 11. This dye is prepared by dissolving 5 g. sulfanilic acid in a minimum amount of sodium carbou- metaphenylenediamine in 25 to 50 cc. water, stir in 3 g. ate solution of moderate strength, adding 2 g. sodium sodium nitrite until dissolved, and then acidify with nitrite dissolved in a little water, and barely acidifying dilute hydrochloric acid. The dye forms as a brown with dilute hydrochloric acid. (Solution A) This powder which should be filtered off, drained, dried, and solution must be kept cold, a t least below room tem- saved. I t may he applied to wool in ,the same manner perature. A few bits of ice added to the solution will as the preceding dyes. The process of adding sodium nitrite and acid to the insure the proper temperature. Dissolve 4 g. beta naphthol (commonly called BN) in as little dilute original intermediate is called "diazotization" from the sodium hydroxide as possible. (Solution B) Pour solu- French word for nitrogen which is "azote"; diazotization A slowly with stirring into solution B; stir well, tion is therefore the introduction of two nitrogen atoms and let stand overnight. A thick mass of dyestuff with the linkage -N =N-. One might suppose that a substance which gave a should form. Transfer the product to a filter and let drain, using gentle suction if i t is available. Finally colored solution would be a dye. Let us find out. the dry dye is powdered and sifted through cheesecloth. Soak a piece of wool yam in water and boil in a red In applying a dye to any textile always observe the rule solution of potassium dichromate. The wool is not to wet the goods thoroughly in water, otherwise the colored. Now let us immerse the skein after squeezing in a solution of lead nitrate or lead acetate. Yellow color does not apply evenly. To apply Orange I1 to a skein of wool, make a bath lead chromate is precipitated on goods, but this is not of 100 cc. water and enough of the dye to give a good strictly a dyeing operation; it is a simple case of the color. Add a few drops of dilute acetic acid to brighten formation on the goods of a colored insoluble compound. It is also of interest to note that certain dyes which the color. Now immerse the wet-out skein of white wool yam, making sure that all parts of the skein are are "fast" on wool have little or no effect on cotton. under the surface of the dye liquid, and bring to a boil, Wet out a skein of cotton and one of wool and immerse frequently moving the skein about in the bath and tum- them in a bath of Cyanole Fast Green and boil. The ing i t over to get an even color. Finally remove the wool takes the color completely and the dye will not (Conlimed on page 386) skein, using a glass rod bent a t one end like the letter J, 3tio
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DYES AND DYEING FOR B13GINNERS (Continuedfrom page 380) wash out. The cotton is only slightly tinted, and this tint may be removed by washing with hot water and soap. Equally curious is the following: immerse wet-out skeins of wool and cotton in a hath of Diamine Fast Yellow and hoil. The cotton takes the color while the wool is very little affected; wash with soap and water and all of the color will come out of the wool but not out of the cotton. And here is a surprising experiment. Thread a needle with fine wool yarn and embroider any design on a square of white cotton cloth. Wet out and immerse in a bath of water containing both the Green and the Yellow mentioned above; bring to a hoil. The goods will come out in two colors, green on the wool and yellow on the cotton. Chrysamine, a cotton color, is prepared as follows: Dissolve 2 g. henzidine in 30 cc. hot water containing 2 cc. concentrated hydrochloric acid. Cool to room temperature or below, and add 1.5 g. sodium nitrite dissolved in a little water. Pour this solution into one of 3.5 g. salicylic acid dissolved in 20 cc. water containing 1 g. sodium hydroxide. Stir well and let stand overnight. Drain on filter, dry, and presewe. This color dyes cotton yellow in a hot hath of water and soap. The developed colors afford a pleasing surprise. Boil a strip of cotton in a solution of BN made alkaline with just enough sodium carbonate to cause complete solution. Remove, squeeze, and dry in the dark. Now prepare a bath of paranitranilime with hydrochloric acid and sodium nitrite, cold; lower the dried cloth into this solution and note the remarkable effect. Some of these diazo compounds are quite sensitive to heat and to light. Because of the heat effect, the diazo compound must be kept cold, and colors so derived are often called "ice colors." Dye a six-inch square of white cotton cloth in Primuline, boil, remove, squeeze, and immerse in water in a beaker; add a gram or so of powdered sodium nitrite, stir, and acidify with dilute hydrochloric acid; a deepening of color will be noted. Remove the cloth, spread i t out on a flat board, cover with a glass plate and cardboard stencil, and expose to bright sunshine for a t least one minute. Return
to the laboratory, and immerse the c l o a in a slightly alkaline solution of BN. The exposed portions will not develop, while the covered parts develop a deep red. Wash, dry, iron out, and preserve. The property of capillarity is shown in textiles by dyeing a long narrow strip of cotton cloth in Congo Red, with a little sodium carbonate solution added to brighten the color. Remove, squeeze, and dry. Support the dry cloth so that it hangs vertically with the lower end just dipping into some dilute hydrochloric acid in a small beaker. As the acid slowly climbs up the cloth the color changes. Indigo Dyeing. Indigo is one of the oldest dyes. F i s t prepare an eight-inch square of white cotton cloth and attach to each of two adjacent corners a twelve-inch length of thread. Soak the cloth in water. In 100 cc. water dissolve just enough indigotine to give a good blue color. Heat and add a few drops of dilute sodium hydroxide, and then stir in little by little some sodium hydrosullite, Na2S20,, until the blue color disappears and a yellowish liquid forms; this is leucoindigo. Now remove the cloth and introduce it into the leuco-indigo solution in a flask, letting the two strings hang outside. Bring to a boil, making sure all of the cloth remains under the surface of the liquid all the time. Finally withdraw the cloth by the threads and hang up in the air. The blue color will gradually develop by oxidation. Alkali Blue. Make a bath of Alkali Blue in 100 cc. water and add sodium carbonate enough to make the liquid quite alkaline. Immerse a long skein of white wool in the liquid and bring to a hoil. Meanwhile fill a tall graduated cylinder with water and with 10 cc. concentrated hydrochloric acid. Remove the wool, squeeze, and lower into the cylinder. The colorless wool becomes a beautiful blue. In an alkaline solution the color does not develop, but it will do so as soon as the skein is made acid. Nicholson's Blue will give the same effect as Alkali Blue. The above experiments are intended merely to arouse the interest of the student in the study of dyes and dyeing. They are in no sense a treatise on the subject; that would come later in the textile school or elsewhere.
