What distinguishes industrial salt from food-grade salt in China's market?

What distinguishes industrial salt from food-grade salt in China's market?
A common misconception is that industrial salt refers to sodium nitrite, but in practice, industrial salt is primarily sodium chloride with lower purity than food-grade salt. Industrial salt, often directly sun-dried sea salt, may contain iron, calcium, magnesium, and potassium impurities, giving it a yellowish or pinkish hue and a tendency to absorb moisture, forming larger crystals. It is used extensively in boiler water softening, chlor-alkali electrolysis, and as feedstock for soda ash production. Food-grade salt undergoes additional purification and often iodization, meeting stricter standards for heavy metals and contaminants. The price difference is notable: food-grade iodized salt retails around 3.5 yuan per 500g, while bulk industrial salt sells for a fraction of that, typically under 300 yuan per tonne. This purity gap drives separate supply chains, with industrial salt sourced directly from salt lakes or sea salt fields, while food-grade salt requires refining and packaging facilities.