Comparison and Application of Methods for Determination of Pigment Water Solubility

The determination of water-soluble substances in the pigment industry is essential to ensure product quality. This article will discuss two widely used methods for the determination of water-soluble substances: cold extraction and thermal extraction, analyze their principles, instruments and materials, and experimental procedures, and explore their application fields.

Part I: Introduction

In the pigment industry, water-soluble matter is a key performance parameter. The content of water-soluble matter affects the use and performance of pigments. In order to accurately determine the content of water-soluble matter in pigments, a variety of different methods have been developed, the most common of which are cold extraction method and thermal extraction method. The two methods differ in principle and application, and this paper will compare and analyze them.

Part II: Cold extraction

Scope and description: The cold extraction method is used to determine the soluble content of pigment samples in cold water. This method is suitable for certain inorganic pigments such as cobalt blue, molybdenum chrome orange and lead chrome yellow.

Instruments and materials: laboratory analytical instruments, membrane filters, evaporation dishes, water, etc.

Determination method: The sample is mixed with water, stirred continuously for 1 hour, then filtered and the filtrate is evaporated to a constant weight. The final water-soluble content is determined by several heating and cooling processes.

The results show that the content of water-soluble substances is expressed by mass and is usually reported as a percentage.

Reference standard: GB 5211.1-2003 "Determination of pigment water soluble matter - cold extraction method".

Part III: Thermal extraction

Scope and description: Thermal extraction is used to determine the soluble content of pigment samples in boiling water. This method is suitable for most inorganic and organic pigments.

Instruments and materials: laboratory analytical instruments, membrane filters, evaporation dishes, water, etc.

Method of determination: Mix the sample with water, boil for 5 minutes, then cool. Filter the filtrate and evaporate to constant weight. The final water soluble content is determined by several heating and cooling processes.

The results show that the content of water-soluble substances is expressed by mass and is usually reported as a percentage.

Part IV: Comparison and Application

Cold extraction is suitable for some specific inorganic pigments, such as cobalt blue, molybdenum chrome orange, etc. It is a relatively simple method, but requires a long stirring and evaporation process.

Thermal extraction is suitable for most inorganic and organic pigments and is a relatively fast method that requires only a short boiling time.

Which method to choose depends on the type and nature of the pigment, as well as the time and resource constraints of the experiment. It is important to note that different methods may result in slightly different results, so it is necessary to indicate the method used when reporting the water soluble content.

Part V: Conclusion

The determination of pigment water solubility is a key step in ensuring product quality. Cold extraction and thermal extraction are two commonly used methods, each with its own scope of application. The correct selection and application of these methods is essential for the pigment industry to ensure that products meet specific requirements, improve product performance, reduce costs, and reduce adverse environmental impacts. At the same time, comparing the two methods helps to determine which method is more suitable for a specific pigment type.