Caustic soda is sold in several grades. The chemical is the same, sodium hydroxide, but the purity, the impurity limits and the paperwork differ, and so does the price. Buying the right grade avoids both quality problems and paying for purity you do not need.

Technical (industrial) grade

The grade used by most industry: cleaning, water treatment, textiles, soap and detergent making, metal treatment and chemical processing.

• Typically flakes or pearls of about 98 to 99% NaOH, or 48 to 50% liquid.
• Specified limits for carbonate, chloride and iron.
• Supplied with a safety data sheet and a certificate of analysis.

Food grade

For use in food processing where caustic is added to food or may leave residues, such as lye peeling, some cocoa and olive processing, and pH adjustment.

• Meets a recognised food additive specification.
• Tighter limits on heavy metals, arsenic, mercury and other impurities.
• Produced and handled under food safety controls, with traceable batch certificates.

Pharmaceutical grade

Meets pharmacopoeia standards (for example BP or USP) for use in medicines and some personal care products, with the strictest documentation.

Laboratory grades: AR and LR

• AR (analytical reagent): high purity with a detailed impurity analysis, for analytical work and standard solutions.
• LR (laboratory reagent): good purity for general lab use where trace impurities matter less.

Lab grades are usually pellets in small containers and cost far more per kg than technical flakes.

How to choose

Use	Grade
Industrial cleaning, CIP with full rinse, water treatment, textiles	Technical
Direct food contact or food additive use	Food grade
Medicines and regulated personal care	Pharmaceutical
Analysis, titration standards	AR
General laboratory use	LR

Always check the COA

Whatever the grade, ask for the batch certificate of analysis and compare it with your specification. For an example COA for technical caustic soda flakes 99%, available to buyers in Oman, see muscatchemical.com/caustic-soda.