ISO 2122:1972

Overview

ISO 2122:1972 is an international standard developed by the International Organization for Standardization (ISO) that specifies a precise method for the preparation of sodium and potassium silicate solutions, particularly focusing on products that are not easily soluble in boiling water. The standard details the procedures for dissolving such silicates and accurately determining the matter insoluble in water. This ensures reliable and consistent quality control of silicate products used in various industrial applications.

This method applies to sodium silicates with the general formula M₂O · xSiO₂ where x ranges between 1.5 and 3.5, and potassium silicates where x ranges between 1.9 and 3.9. The process involves sample sieving, dissolution under controlled pressure and temperature conditions using an autoclave, filtration, and subsequent gravimetric analysis of insoluble matter. The standard is essential for laboratories and industries dealing with silicate products requiring standardized testing methods.

Key Topics

• Scope of Application
  The standard is designed for sodium and potassium silicates used industrially, with specific ranges of silica modulus (x values). It addresses the challenge of dissolving fine particles that are difficult to solubilize in boiling water.

• Sample Preparation
  Samples must be sieved to remove fine particles before dissolution, ensuring uniformity and accuracy in testing.

• Dissolution Procedure
  The silicate sample is dissolved in carbon dioxide-free water inside a stainless steel autoclave heated to specific temperatures (135–160 °C for sodium silicates, 150 °C for potassium silicates) under approximately 6 bars pressure.

• Filtration and Insoluble Matter Determination
  After dissolution, the solution is vacuum-filtered through a tared filter crucible with defined porosity. The insoluble residue is washed, dried, and weighed to calculate the percentage of insoluble matter by mass.

• Preparation of Test Solutions
  The filtrate is diluted to a predetermined volume, forming a uniform solution for further chemical analyses or tests.

• Reagents and Apparatus

  • Carbon dioxide-free water, prepared by boiling or bubbling inert gas
  • pH indicator paper for monitoring neutrality
  • Stainless steel autoclave suited for 6-bar pressure
  • Porous fritted crucibles and ashless filter paper for filtration

• Special Cases
  Adaptations of the dissolution method are included for silicates with silica moduli exceeding the specified ranges, using alternative filtering methods and varying autoclave parameters.

• Expression and Reporting of Results
  The standard provides formulas and guidelines to express the insoluble content quantitatively and mandates detailed test reports documenting procedures, results, and any deviations.

Applications

ISO 2122:1972 is critical in industries and laboratories where precise quality evaluation of sodium and potassium silicates is required. Practical applications include:

• Industrial Quality Control
  Ensuring raw materials and products meet solubility and purity specifications essential for manufacturing processes.

• Research and Development
  Supporting formulation and testing of silicate-based materials with consistent and reproducible analytical methods.

• Chemical Analysis Laboratories
  Serving as a standardized reference method for determining insoluble matter content, which influences product performance and safety.

• Process Optimization
  Helping manufacturers adjust production parameters to minimize insoluble residues, enhancing product consistency.

Related Standards

For comprehensive analysis and testing of sodium and potassium silicates, ISO 2122:1972 should be considered alongside:

• ISO/R 1686 – Sampling and general test methods for sodium and potassium silicates
• ISO/R 1690 – Gravimetric determination of silica content by insolubilization
• ISO/R 1691 – Gasometric determination of carbon dioxide content expressed as sodium or potassium carbonate

These related standards complement ISO 2122 by covering broader aspects of silicate composition analysis and sampling techniques.

Keywords: ISO 2122:1972, sodium silicates, potassium silicates, industrial silicates, solution preparation, insoluble matter determination, autoclave dissolution, silicate solubility testing, chemical analysis, quality control of silicates, standard test method, filtration, gravimetric analysis.