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Developing an activity that can relate chemistry concepts to that which is interesting and relevant to high school students is a challenging one, but tie dyeing is one of those phenomena that has been found to be very popular and successful in many high schools. Even though it appears to be an "arts and crafts" project, the activity can be justified in a high school chemistry course if the chemistry involved in tie dyeing can be related to the organic chemistry unit. The objective of this article is to describe the method of application and the chemistry of the most popular fiber reactive dyes, Procion[1] MX dyes, used in tie dyeing.
The Dyes
Procion MX is the commercial name for dichlorotriazine dyes. They are the most reactive and versatile of the fiber reactive dyes, which means that the dye molecule actually reacts with fabric molecules. These dyes can be used an cotton, silk, wool, rayon, linen, paper, and wood but not on synthetic fibers. The reactive group is shown below in Figure 1 (1). (Figure 1 omitted)
The "D" represents the color-forming or chromophore part of the molecule attached to the reactive group. Examples of three of these common dyes are given in Figure 2 (2). (Figure 2 omitted)
Mixing the Dyes
* Caution: The dyes are sold in the form of a powder and are considered to be nontoxic. Common sense should be used in handling any chemical, however. Prolonged inhalation of the dye powder can cause an allergic reaction in some people. A dust mask and rubber gloves should be worn to mix the chemical, and mixing should be done in a hood.
Approximately 10-20 mL of dye may be mixed with 250 mL of warm water or urea solution. Hot water up to 120deg F may be used to dissolve the less soluble...