Chlorine Cl 17

This lesson explores the role of chlorine in pigments identification, focusing particularly on modern chemistry pigments such as phthalocyanine pigments. Although chlorine is not a key element in pigment identification overall, it plays an essential role in specific pigments, including phthalo green. Chlorine’s detection through XRF spectroscopy is examined, with a focus on the use of different X-ray tube filter setups to optimize its identification.

Objectives

  • Understand the significance of chlorine in pigment analysis, particularly in modern chemistry pigments.
  • Learn how chlorine is detected using XRF spectroscopy and its X-ray energy characteristics.
  • Compare the effectiveness of different X-ray tube filter setups for identifying chlorine.
  • Analyze real-life examples of chlorine detection in sodium chloride and phthalo green pigments.

Materials

Lesson Plan

1. Introduction to Chlorine in Pigments
  • Discuss the role of chlorine in modern pigments, particularly phthalocyanine pigments.
  • Demonstrate the use of an attenuation calculator to determine chlorine x-ray transmission through 10 mm of air.
3. X-ray Tube Filter Setups
  • Review the three X-ray tube filter setups:
    • No filter: Optimal for energies below 2.5 keV.
    • Low-keV filter: For 2.5–10 keV.
    • Routine filter: Suitable for higher energy ranges but less effective for chlorine.
  • Discuss the borderline nature of chlorine’s energy (2.6 keV) and the choice of filter depending on the situation.
4. Lab Activity 1: Sodium Chloride Spectrum Analysis
  • Introduce sodium chloride as the simplest material to detect chlorine.
  • Acquire spectra using the three filter setups:
    • No filter: High peak (~100,000 counts).
    • Low-keV filter: Detectable peak (~5,000 counts).
    • Routine filter: No detectable chlorine peak. 
5. Lab Activity 2: Phthalo Green Spectrum Analysis
  • Analyze phthalo green as a real-world pigment sample containing chlorine.
  • Compare spectra obtained with different filter setups:
    • No filter: Strong chlorine peak (~80,000 counts).
    • Low-keV filter: Adequate chlorine peak (~2,000 counts).
    • Routine filter: Reduced or almost undetectable chlorine peak.
  • Conclude that the no-filter or low-keV setup is optimal for detecting chlorine in phthalo green.
 

To reinforce the concepts discussed here, we also provide a video lesson that visually walks through the key points of this topic. Watching the video alongside the text can help you better understand and apply these ideas in practice.

XRF Spectroscopy for Art Examination

The course XRF Spectroscopy for Art Examination introduces conservators, art historians, and scientists with interest in Art to the principles and practical applications of X-ray fluorescence (XRF) spectroscopy in the examination of artworks. The course starts with basic principles of XRF and gradually explores its role in identifying materials and methods used in the creation and conservation of art.

Course Objectives

  • Understand the fundamentals of XRF spectroscopy and how it applies to the analysis of art.
  • Learn the key features and limitations of XRF for examining art and archaeology.
  • Gain skills in interpreting XRF spectra to identify specific elements in paint layers, inks and metals.

Training 2026

Scientific Art Examination – Resources:
Getty Conservation Institute (GCI) – USA
The British Museum – Scientific Research Department – UK
Scientific Research Department – The Metropolitan Museum of Art, New York, USA
C2RMF (Centre de Recherche et de Restauration des Musées de France) – France
Rijksmuseum – Science Department – Netherlands

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