In analytical chemistry, ash is the name given to all non-aqueous residue that remains after a sample is burned, and consist mostly of metal oxides.

Ash is one of the components in the proximate analysis of biological materials, consisting mainly of salty, non-organic constituents. It includes metal salts which are important for processes requiring ions such as Na⁺ (Sodium), K⁺ (Potassium), Ca²⁺ (Calcium). It also includes trace minerals which are required for unique molecules, such as chlorophyll and hemoglobin.

For instance, the analysis of honey shows:

Typical honey analysis

• Fructose: 38%
• Glucose: 31%
• Sucrose: 1%
• Water: 17%
• Other sugars: 9% (maltose, melezitose)
• Ash: 0.17%

Source: Sugar Alliance

In this example the ash would include all the minerals in honey.

Also see:

• oxides, e.g. Al₂O₃, CaO, Fe₂O₃, MgO, MnO, P₂O₅, K₂O, SiO₂
• carbonates: Na₂CO₃ (aka soda ash), K₂CO₃ (aka potash),
• bicarbonates, e.g. NaHCO₃ (aka baking soda),
• Sulfates: sulfate ash according to Ph. Eur.

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