2 examples of solid dissolved in solid
Brass and steel are classic solid-in-solid solutions: one metal dissolves in another (brass), and a small atom dissolves into a metal lattice (steel).
Solid dissolved in solid in solution language
A solid solution is a single solid phase in which atoms of a solute are distributed within the crystal lattice of a solvent. The phrase “dissolved” refers to atomic-level mixing that remains uniform on the scale of many unit cells.
Composition can be described in several ways (mass percent, atom percent, mole fraction). Mole fraction expresses the fraction of particles that belong to each component:
\[ x_i=\frac{n_i}{\sum n_j}. \]
Two common examples
- Brass (Zn in Cu): zinc atoms replace some copper atoms in the metal lattice, creating a substitutional alloy (solid solution).
- Steel (C in Fe): carbon atoms occupy interstitial sites (small “holes”) in the iron lattice, creating an interstitial solid solution.
Both materials behave as single phases over important composition ranges, with properties that vary smoothly with composition. The solute atoms are incorporated into the solid structure rather than forming a separate macroscopic phase.
Atomic picture of substitutional and interstitial mixing
Comparison of the two examples
| Example | Solid solvent (host) | Solid solute | Solid-solution type | Atomic-scale description |
|---|---|---|---|---|
| Brass | Copper (Cu) | Zinc (Zn) | Substitutional | Zn atoms occupy Cu lattice sites in a single metallic phase over broad ranges. |
| Steel | Iron (Fe) | Carbon (C) | Interstitial | C atoms sit in interstitial sites of the Fe lattice at relatively low mole fraction. |
Solid solution versus compound
A solid solution has variable composition, often expressed as a range, and preserves the basic lattice type of the host over that range. A compound has fixed stoichiometry and a distinct crystal structure tied to that stoichiometry.
Common pitfalls
- Mixture versus solid solution: a uniform alloy is a single phase; a visible blend of phases is not a single solid solution.
- Any two solids: complete miscibility is uncommon; atomic size, bonding, and crystal structure constraints limit solubility in solids.
- “Dissolved” meaning: the relevant scale is atomic dispersion in the lattice rather than macroscopic melting into a liquid.