Page 225 - Basic Principles of Textile Coloration

214 DYEING THEORY

techniques. Aggregation numbers – the average number of dye molecules in a
micelle – had been determined from diffusion coefficients, electrical conductivity
measurements, osmotic pressures, membrane filtration, and light scattering.
Almost all the data are of limited accuracy for one reason or another. Aggregation
increases with increasing dye concentration and decreases with increasing
temperature. Exact aggregation numbers and the number of incorporated counter
ions, which determine the actual overall electric charge of the micelle, are
imprecisely known. It is usually assumed that a rapid exchange occurs between
free dye molecules in the solution and dye micelles of various sizes.

11.4 CONCLUSION
Opinions about the value of dyeing theory as a tool for developing dyeing
technology are just as varied as those related to political parties. Much of dyeing
theory is difficult to understand without an extensive background in physical
chemistry. The results are often in a form that seems quite unrelated to practical
dyeing. Nevertheless, dyeing is a reversible process governed by the fundamental
laws of thermodynamics and kinetics. Studies in these areas, while they might
seem far removed from the reality of the dyehouse, do explain the phenomena that
are occurring. The problem is that textile dyeing occurs in a complex
heterogeneous system. A dye solution does not behave like a simple solution of
sodium chloride. The distribution of a dye between solution and a heterogeneous
fibre is not the same as the partition of, say, benzene between water and hexane.
Unfortunately, textile dyeing is complex and not easily amenable to simple
experimental studies. Similarly, dyeing theory does not always provide simple
conclusions.

REFERENCES

1. C L Bird and W S Boston, Eds., The Theory of Coloration of Textiles (Bradford: SDC, 1975).
2. J Steinhardt and M Harris, J. Res. Nat. Bur. Standards, 24 (1940) 335.
3. A Johnson, Ed, The Theory of Coloration of Textiles, 2nd Edition (Bradford: SDC, 1989).
4. R H Peters, Textile Chemistry, Vol. III – The Physical Chemistry of Dyeing (Amsterdam: Elsevier, 1975).