Understanding Purity Standards for Salt
Purity standards for salt (sodium chloride, NaCl) ensure safety, quality, and suitability for various applications, from food to industrial use. International bodies like the World Health Organization (WHO), Food and Drug Administration (FDA), and Codex Alimentarius set these benchmarks to regulate impurities such as heavy metals, sulfates, and moisture.
Key Purity Levels:
- Food-grade salt: Minimum 97-99% NaCl, with limits on insoluble matter (<0.5%) and magnesium (<0.1%).
- Pharmaceutical-grade salt: >99.5% NaCl, tested for microbial contamination and endotoxins.
- Industrial salt: 95-98% NaCl, allowing higher impurities for uses like de-icing.
For example, in food production, exceeding sulfate limits ($SO_4^{2-}$ > 0.1%) can affect taste and texture, leading to product recalls. These standards promote global trade by harmonizing quality expectations.
Inline concentration example: Purity is often expressed as $ \frac{\text{mass of NaCl}}{\text{total mass}} \times 100\% $.