Related Experiment Video
Updated: Feb 28, 2026
11:27
A Package of Established Analytical Tools to Investigate the Solid-State Alteration of Lipid-Based Excipients
Published on: August 9, 2022
2.6K
Lead(ii) soaps: crystal structures, polymorphism, and solid and liquid mesophases
F J Martínez-Casado1, M Ramos-Riesco, J A Rodríguez-Cheda
1MAX IV Laboratory, Lund University, Fotongatan 2, SE-225 94 Lund, Sweden. francisco.martinez@maxiv.lu.se.
Physical Chemistry Chemical Physics : PCCP
|June 22, 2017
Summary
Long-chain lead(II) soaps, from octanoate to octadecanoate, were characterized. Their solved crystal structures can serve as fingerprints for detecting these compounds in artworks.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Art Conservation Science
Background:
- Lead(II) alkanoates, commonly known as lead soaps, are long-chain compounds.
- These compounds are relevant to art conservation as they can form as degradation products in oil paintings.
Purpose of the Study:
- To thoroughly characterize the long-chain lead(II) alkanoates (octanoate to octadecanoate) across all their phases and mesophases.
- To solve the crystal structures of these compounds at room temperature.
- To explore the potential of using structural data for detecting lead soaps in artworks.
Main Methods:
- X-ray Diffraction (XRD)
- Pair Distribution Function (PDF) analysis
- Differential Scanning Calorimetry (DSC)
- Fourier-Transform Infrared Spectroscopy (FTIR)
- Solid-State Nuclear Magnetic Resonance (ssNMR)
Main Results:
- Crystal structures at room temperature were solved, revealing two polymorphic forms in the crystal phase for nonanoate and decanoate, exhibiting monotropic polymorphism.
- At higher temperatures, lead soaps exhibit a rotator solid mesophase, a liquid crystal phase, and a liquid phase, all with similar local arrangements.
- Pair distribution function analysis shows consistent short-range order across different members within the same phases and mesophases.
Conclusions:
- The solved crystal structures of lead(II) soaps can serve as fingerprints for their detection in oil paintings using XRD.
- PDF analysis shows potential for detecting lead soaps in disordered phases or during early stages of formation in paintings due to consistent short-range order.
Related Concept Videos
01:24Solid–Solid Solutions
18
The temperature-composition phase diagram of two solids, A and B, which are immiscible in the solid phase but form miscible liquids, shows that when the temperature is low, these two exist as separate, pure solids (A and B). As the temperature increases, they transition into a single-phase liquid solution where A and B coexist. Moving from point a1 to a2 in the phase diagram, the composition changes such that solid B begins to separate from the solution, enriching the remaining liquid with A.
18
02:54Molecular and Ionic Solids
20.5K
Crystalline solids are divided into four types: molecular, ionic, metallic, and covalent network based on the type of constituent units and their interparticle interactions.
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
20.5K
02:37Metallic Solids
21.1K
Metallic solids such as crystals of copper, aluminum, and iron are formed by metal atoms. The structure of metallic crystals is often described as a uniform distribution of atomic nuclei within a “sea” of delocalized electrons. The atoms within such a metallic solid are held together by a unique force known as metallic bonding that gives rise to many useful and varied bulk properties.
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability....
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability....
21.1K
01:10Recrystallization: Solid–Solution Equilibria
4.1K
Recrystallization is a purification technique used to separate impurities from solid compounds. In this technique, no chemical reactions occur. Instead, it exploits physical properties only, specifically, the solubility differences between the desired compound and impurities, either at a single temperature or at different temperatures, and under other selected conditions. The solid-solution equilibrium (solubility equilibrium) of each component in the solution represents a binary phase...
4.1K
01:27Two Components: Liquid–Liquid Systems
27
A pressure-composition phase diagram explicitly describes the behavior of an ideal solution of two volatile liquids under varying pressures and compositions. A pressure-composition diagram has two main curves. The bubble point curve represents the plot of pressure versus liquid mole fraction. It indicates the pressure at which the first bubble of vapor forms from the liquid phase as the system pressure decreases.The dew point curve is the pressure versus vapor mole fraction. It indicates the...
27
02:22Structures of Solids
19.8K
Solids in which the atoms, ions, or molecules are arranged in a definite repeating pattern are known as crystalline solids. Metals and ionic compounds typically form ordered, crystalline solids. A crystalline solid has a precise melting temperature because each atom or molecule of the same type is held in place with the same forces or energy. Amorphous solids or non-crystalline solids (or, sometimes, glasses) which lack an ordered internal structure and are randomly arranged. Substances that...
19.8K