This lesson explores the role of phosphorus in art examination, focusing on its detection through X-ray fluorescence (XRF) spectroscopy. Using a guitar nut made of bone and other materials rich in phosphorus, we will analyze how XRF spectroscopy can distinguish pigments containing phosphorus from those that do not.
Objectives
- Understand the chemical properties and significance of phosphorus (atomic number 15) in art materials.
- Learn to interpret XRF spectra, particularly in identifying phosphorus in different substances.
Materials
- Sample materials: monopotassium phosphate, guitar nut (bone), bone black pigment, vine black pigments from PIGMENTS CHECKER
Lesson Plan
1. Introduction to Phosphorus and Its Role in Art Materials
- Highlight the significance of phosphorus in materials like bone and its applications in art and pigments.
- Discuss the K alpha line of phosphorus at 2 keV and its relevance to XRF analysis.
- Use an online calculator to determine the transmission of 2 keV X-rays through 10 mm of air at normal pressure.
- Analyze the results, focusing on the detection feasibility of phosphorus under these conditions.
2. Experiment 1: Analyzing Monopotassium Phosphate
- Examine the XRF spectrum of monopotassium phosphate, noting the strong phosphorus peak at 2 keV.
- Discuss why this material is ideal for detecting phosphorus due to its composition.
3. Experiment 2: Testing a Guitar Nut Made of Bone
- Analyze the spectrum of the guitar nut and compare its phosphorus peak to that of monopotassium phosphate.
4. Experiment 3: Differentiating Bone Black from Vine Black
- Analyze the XRF spectra of bone black and vine black pigments.
- Highlight the presence of phosphorus in bone black and its absence in vine black.
- Discuss the significance of this distinction in identifying pigments in art examination.
