Introduction and role of Sodium Dithionite

Sodium dithionite, commonly known as "insurance powder," is a white or grayish-white crystalline powder with strong reducing properties. Here is an introduction and its functions:

1. Chemical Properties: The chemical formula of sodium dithionite is Na2O4S2, with a molecular weight of 174.12, and the CAS number is 7775-14-6. It is soluble in water and ethanol and reacts strongly with water.

2. Preparation and Commercial Products: Sodium dithionite is available for sale from reagent companies both domestically and internationally. It is a very inexpensive reducing agent.

3. Functions:

  - Textile Industry: It is widely used in the textile industry for reductive dyeing, reductive cleaning, printing, and decolorization, as well as for bleaching silk, wool, and nylon fabrics. Since it does not contain heavy metals, the fabrics bleached with it have bright colors that are not prone to fading.

  - Pulp Bleaching: As a reductive pulp bleaching agent, it improves the whiteness of the pulp by reducing end saturated carbonyl groups, reducing quinone structures in the pulp, and reducing Fe3+ to Fe2+.

  - Food Preservation: In the field of food preservation, it utilizes the SO2 released upon contact with moisture to inhibit the reproduction of aerobic molds and absorb oxygen, extending the shelf life of foods such as lychees.

4. Safety and Precautions:

  - Sodium dithionite is highly reactive, flammable, and hygroscopic. It should be stored in a dry and cool place.

  - It has a destructive effect on most dyes except for reduction dyes, so it is generally only suitable for use on white textiles.

  - Due to the production of toxic sulfur dioxide gas upon decomposition, appropriate safety measures must be taken when handling sodium dithionite.

5. Other Uses: Sodium dithionite is also used as a tanning agent in the leather industry and as a reducing agent in the pharmaceutical and kaolin industries.

6. Environmental Impact: The production process of sodium dithionite generates a certain amount of waste liquid and wastewater. These wastewaters have high salt content and chemical oxygen demand (COD), posing a burden on the environment.

Sodium dithionite plays an important role in various industries due to its strong reducing properties and low cost, but it is also important to pay attention to its safe use and potential environmental impact.