Analysis of common chemicals used in textile wet processes

Chemical analysis always involves the use of different chemicals. In order to assure accurate analysis results, the chemicals used need to he standardised, the procedures must he followed exactly and the data obtained have to he analysed statistically. If an instrument is used, it should be maintained and calibrated properly. A detailed description of analytical chemistry is not the purpose of this book. Readers can refer to analytical chemistry books in the literature. During the last five decades, sophisticated instruments in the market have made chemical analysis much easier than before. However, the price of the instruments plus high operation costs have limited their applications in many textile businesses. Therefore, the analytical methods discussed in this chapter are mainly those of traditional wet chemistry based analyses. 

In a chemical analysis, especially involving quantitative analysis, the amount of chemical used is critical and can be determined by the measurement of concentration if it is a solution, or by weight, if it is a solid. Sometimes, the concentration of a solution can be easily determined by using another known solution through titration. For acids and bases, if the concentration is sufficiently low, the pH concept is generally used to represent the concentration of the acid or base in the aqueous solution. For the analysis of common chemicals, such as caustic soda, acetic acid, soda ash, sodium dithionite, hydrogen peroxide, and so on, titrimetric analysis and gravimetric analysis are widely used. For the analysis of surfactants and other chemicals, qualitative spot tests and specialised instruments should be utilised. 

The concentration of a solute is usually expressed as the amount of a solute in a unit volume of a solution. The amount of a solute can be in grams (g), kilograms (kg), moles (mol), or normals (n). The unit volume of a solution is always in litres (1). A 

The conversion among these concentrations can be carried out by using the following equations  

Titration is a method by which the concentration of an unknown solution can be determined using a standardised solution with a known concentration through a stoichiometric reaction. The end point of the chemical reaction is indicated by the colour change of an indicator or an instrumental reading. The standard solution of a known reagent is the titrant and the unknown solution is the titrand. The unknown concentration can be determined using Equation [4.3]  

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Analysis of common chemicals used in textile wet processes... 

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