HS Code 28.31 – Dithionites and sulphoxylates

HS code 2831 is a 4-digit heading in the Harmonized System that covers: Dithionites and sulphoxylates. HS Code 2831 encompasses dithionites and sulphoxylates, a critical category of inorganic chemicals known primarily for their powerful reducing properties. These compounds, such as sodium dithionite and sodium formaldehyde sulphoxylate, are vital across various industrial sectors. Dithionites are widely utilized in the textile industry for vat dyeing, reductive clearing, and stripping, as well as in the pulp and paper industry for bleaching mechanical pulp. Their strong reducing power makes them indispensable for achieving desired color and brightness in these processes. Sulphoxylates, on the other hand, find significant application as polymerization initiators and in the production of synthetic rubber and plastics, acting as effective reducing agents in various chemical syntheses. This heading's scope includes the chemically defined salts of dithionous acid and sulphoxylic acid, ensuring a precise classification for these specialized compounds. Understanding this classification is crucial for trade compliance, as it dictates applicable tariffs, duties, and regulatory requirements, particularly concerning hazardous material handling and environmental regulations. Historically, the demand for these chemicals has been closely linked to the growth of the textile and polymer industries, making them significant commodities in international trade. As part of Chapter 28, which covers inorganic chemicals, this heading provides a specific classification for these sulfur-oxygen compounds, distinguishing them from other sulfur derivatives based on their unique chemical structure and reducing capabilities.

Sodium dithionite, Zinc dithionite, Magnesium dithionite, Calcium dithionite, Sodium formaldehyde sulphoxylate, Zinc formaldehyde sulphoxylate, Calcium formaldehyde sulphoxylate, Ammonium dithionite, Potassium dithionite, Lithium dithionite, Hydrosulphite, Rongalite, Formosul, Decroline, Reducing agent F, Sodium sulfoxylate formaldehyde, Zinc sulfoxylate formaldehyde, Magnesium sulfoxylate formaldehyde

A common misclassification error involves confusing dithionites and sulphoxylates (2831) with other sulfur-containing compounds like sulphites (2832) or sulphates (2833). Traders might mistakenly classify sodium dithionite as sodium sulfite, or sodium formaldehyde sulphoxylate as a general sulfur compound. The key distinction lies in the specific chemical structure and oxidation state of the sulfur atom. Dithionites contain the S2O4(2-) anion, while sulphoxylates are derivatives of H2SO2. Sulphites (SO3(2-)) and sulphates (SO4(2-)) are chemically distinct, with different industrial applications. Incorrect classification can lead to incorrect duty rates, regulatory non-compliance, and delays, especially given the hazardous nature of some of these chemicals.

In 2025, the top exporters of HS code 2831 in UN Comtrade data were China ($111M, 56% of world exports), India ($39M) and Belgium ($28M). World exports came to about $200M, adding countries' reported figures and partner-based estimates for those that did not report (UN Comtrade data). Countries that did not report 2025 data are estimated from partner records, which can understate them.

In 2025, the top importers of HS code 2831 in UN Comtrade data were Türkiye ($31M, 11% of world imports), Pakistan ($25M) and Vietnam (about $19M). World imports came to about $267M, adding countries' reported figures and partner-based estimates for those that did not report (UN Comtrade data). Countries that did not report 2025 data are estimated from partner records, which can understate them.

HS code 2831 is a 4-digit heading under Chapter 28 of the Harmonized System. The first 2 digits (28) identify the chapter, and digits 3-4 (31) specify the heading. This code contains multiple 6-digit subheadings for precise product classification.