Dithionites and sulfoxylates
3 declarable lines
Heading 2831 covers dithionites (also called hydrosulfites) and sulfoxylates, which are inorganic sulfur-oxygen salts used mainly as reducing and bleaching agents. The heading splits first by metal: lines under 2831.10 are for sodium compounds, and 2831.90.00.00 covers all other dithionites and sulfoxylates. Within the sodium group, sodium formaldehyde sulfoxylate has its own free line, and all other sodium dithionites and sulfoxylates fall on the residual 5.5% line.
Products in this heading
- Sodium dithionite (sodium hydrosulfite), the common reductive bleach for textiles and pulp
- Sodium formaldehyde sulfoxylate
- Zinc dithionite
- Potassium dithionite
- Calcium dithionite
- Sodium sulfoxylate salts used as polymerization activators
How to choose the right subheading
- Identify the metal or cation: sodium compounds go in 2831.10, everything else in 2831.90.
- Confirm the anion is a dithionite (hydrosulfite) or a sulfoxylate, not a sulfite, sulfate or sulfide.
- For sodium products, check whether the goods are sodium formaldehyde sulfoxylate, which has a separate free line.
- Check purity and physical form: aqueous solutions and stabilized powders are classified by chemical identity, not by packaging.
Often confused with
- Heading 2832Sodium sulfite and sodium thiosulfate
Sulfites and thiosulfates are classified in heading 2832, not with dithionites.
- Heading 2830Sodium sulfide and polysulfides
Sulfides contain sulfur but no oxygen, and sit in heading 2830.
- Heading 2833Sodium sulfate
Sulfates are fully oxidized sulfur salts classified in heading 2833.
- Heading 2828Sodium hypochlorite and calcium hypochlorite
These are chlorine-based bleaching agents in heading 2828, often used alongside dithionites.
- Heading 2825Hydrazine and hydroxylamine salts
These are other inorganic reducing bases covered by heading 2825.
Frequently asked questions
What is the HTS code for sodium dithionite?
Sodium dithionite (sodium hydrosulfite) is classified under 2831.10.50.00, the residual line for sodium compounds of this heading. The general (MFN) rate for that line is 5.5%.
What is the duty on sodium formaldehyde sulfoxylate?
Sodium formaldehyde sulfoxylate falls under 2831.10.10.00. The general (MFN) rate for that line is Free.
How do I classify a dithionite that is not a sodium salt?
Non-sodium dithionites, such as zinc or potassium dithionite, go in 2831.90.00.00. The general (MFN) rate for that line is 5.5%.
Guide written from the official schedule text. Rates quoted are general (MFN) rates; check the line page for trade agreement rates and the classification of your exact product.