Sodium thiosulfate brief introduction

Sodium thiosulfate，Also known as sodium sulfite, baking soda, and Haibo (derived from its alias sodium hydrate), with a molecular formula of Na2S2O3 · 5H2O. It is a common thiosulfate, a colorless and transparent monoclinic crystal with a density of 1.667 grams per cubic centimeter. Melting point at standard atmospheric pressure is 48 degrees Celsius. Sodium thiosulfate is soluble in water and reacts with strong acids to produce sulfur and sulfur dioxide

Sodium thiosulfate Basic information

Sodium thiosulfateNumbering system

Sodium thiosulfate Physical and Chemical Properties

Appearance and characteristics:

Colorless crystal or white powder

Density:

1.01 g/mL at 25 °C

Boiling point:

100°C

Melting point:

48°C

Stability:

Stable. Incompatible with strong acids, strong oxidizing agents, iodine, mercury.

Storage conditions:

2-8ºC

security information

• RTECS：

• XN6476000

Safety instructions:

S24/25-S23-S36-S26

Hazard category code:

R36/37/38

WGK Germany：

one

Customs code:

two billion eight hundred and thirty million nine hundred and nine thousand

Dangerous goods signs:

Xi

Production method and purpose

Production method

There are many synthesis methods for sodium thiosulfate, including sodium sulfite method, alkali sulfide method, etc.

1. The sodium sulfite method involves the reaction of a pure alkali solution with sulfur dioxide gas, followed by neutralization with caustic soda, removal of impurities with sulfurized alkali, filtration, and dissolution of sulfur powder in a hot sodium sulfite solution for reaction. After filtration, removal of impurities, filtration, and addition of caustic soda for alkaline treatment, the final product of sodium thiosulfate is obtained through concentration, filtration, crystallization, centrifugal dehydration, and screening. Reaction equation:

2. The sulfide alkali method uses the raw material liquid prepared from the residue of sulfide alkali evaporation and barium sulfide wastewater (containing sodium carbonate and sodium sulfide) to react with sulfur dioxide. After clarification, sulfur powder is added for heating reaction. After evaporation, cooling crystallization, washing, separation, and screening, the finished product of sodium thiosulfate is obtained. Reaction equation:

The raw material used to prepare anhydrous sodium thiosulfate is sodium thiosulfate pentahydrate. Heat the pure pentahydrate sodium thiosulfate crystals to dissolve them completely in their own crystal water, and concentrate them by heating below 100 ℃ until a large amount of anhydrous crystals precipitate. Separate the crystals and dry them below 100 ℃.

4. Adopt dehydration method. Anhydrous sodium thiosulfate crystals are indirectly heated with steam to dissolve in their own crystal water. After concentration, centrifugal dehydration, drying, and screening, anhydrous sodium thiosulfate products are obtained. The reaction equation is as follows.

The main components of the comprehensive method are sodium sulfide, sodium sulfite, sulfur, and a small amount of sodium hydroxide. The feed solution is obtained by vacuum evaporation, activated carbon decolorization, pressure filtration, cooling, crystallization, centrifugal dehydration and screening to obtain the finished product.

6. Sodium sulfate neutralization method, mainly composed of waste materials such as sodium sulfide and a small amount of sodium carbonate.

use to

Mainly used as a fixative in the photography industry. Secondly, when tanning leather, it is used as a reducing agent for dichromate, a neutralizing agent for nitrogen-containing exhaust gas, a mordant, a bleaching agent for wheat straw and wool, and a dechlorination agent for pulp bleaching. It is also used in the manufacturing of tetraethyl lead, dye intermediates, and silver extraction from ores.

toxicity