Sodium thiocyanate CAS:540-72-7

What is Sodium thiocyanate?

Sodium thiocyanate, commonly known as sodium thiocyanate or sodium rhodanide, is an inorganic thiocyanate. Its chemical formula is usually written as:

NaSCN (structural formula Na—S—C≡N, molecular formula CNNaS)

Molecular weight approximately 81.07, CAS number 540-72-7.

It is generally a white orthorhombic crystal or crystalline powder, odorless, and extremely hygroscopic. It is highly soluble in water, with a significant endothermic effect during dissolution (a decrease in solution temperature), and also soluble in organic solvents such as ethanol and acetone; its melting point is approximately 287℃, and it decomposes upon melting. SCN⁻ ions are pseudohalogen ions with strong coordination ability: they can form a blood-red complex with ferric ions (Fe³⁺) and a white precipitate of silver thiocyanate with silver ions (Ag⁺), thus making it an important reagent for detection and titration in analytical chemistry.

From a chemical classification perspective, sodium thiocyanate belongs to the inorganic salt family, specifically the pseudohalides (thiocyanates). Industrially, it is mainly produced by reacting sodium cyanide with sulfur, and can also be recovered as a byproduct from the desulfurization process of coke oven gas.

Industrial-grade sodium thiocyanate refers to sodium thiocyanate products primarily intended for industrial production. Its quality control focus differs from that of reagent-grade and food-grade products.

Industrial-grade sodium thiocyanate typically focuses on the following indicators:

1.Main content and moisture

Industrial applications place greater emphasis on the stability of the content of active ingredients, such as sodium thiocyanate content, moisture, and free alkali. These indicators directly affect the performance consistency and product quality of downstream formulations (such as concrete admixtures and spinning solvents).

2.Iron content

This is a key indicator unique to sodium thiocyanate: iron impurities will form a red complex with SCN⁻, making the product appear reddish, and will also affect its performance in fields sensitive to metal ions such as electroplating and pharmaceuticals. Industrial customers usually have strict upper limit requirements for iron content.

3.Chlorides and sulfates

The content of impurities such as chloride and sulfate affects product purity and may introduce interfering ions into downstream electrolytes, electroplating solutions and other systems, affecting process stability.

4.Water-insoluble matter

Water-insoluble matter reflects the cleanliness of a product and affects the stable operation of solution preparation and continuous processes such as spinning and electroplating.

5.Appearance and color

Industrial customers typically require products to be white or slightly yellow crystals/powder; abnormal color often indicates oxidation, deliquescence, or contamination.

What are the uses of industrial-grade Sodium thiocyanate?

Industrial-grade sodium thiocyanate is used in many industries due to its characteristics of being “easily soluble, pseudohalogen, and having strong coordination”.

1.Concrete early strength agents and antifreeze agents

Sodium thiocyanate is an important component of concrete early strength agents and antifreeze agents. When compounded with lithium sulfate, triethanolamine, etc., it can accelerate cement hydration, improve early strength, and lower freezing point. It is widely used in winter construction, emergency repairs and construction, precast components, and cement grinding aids.

2.Solvent for spinning acrylic fibers

In the production of acrylic fiber (polyacrylonitrile fiber), high-concentration sodium thiocyanate aqueous solution is used as a solvent to dissolve polyacrylonitrile, which is then spun into fibers by wet spinning. This is one of the mature and economical important process routes in the chemical fiber industry.

3.Electroplating and Metal Surface Treatment

Sodium thiocyanate can be used as a component or additive in cyanide copper plating, silver plating, and black nickel plating electrolytes. It can also be used in stripping solutions and metal surface treatments to help improve the uniformity, adhesion, and appearance of the plating layer.

4.Electroless nickel plating stabilizer

In electroless nickel plating systems, sodium thiocyanate can act as a stabilizer and complexing regulator, inhibiting spontaneous decomposition of the plating solution and improving coating quality and process life.

5.Pesticides and Plant Growth Regulation

Sodium thiocyanate can be used to synthesize herbicides and insecticide intermediates. It has also been used as a plant defoliant to help crops such as cotton to defoliate and ripen before mechanized harvesting.

6.Oilfield chemicals

Sodium thiocyanate can be used as a water drive tracer in oilfields, and as an additive in drilling and completion fluids to help monitor water channeling in oil reservoirs and improve drilling fluid performance.

7.Precious Metal Extraction and Beneficiation

Thiocyanate systems can be applied to the leaching and extraction of precious metals such as gold and silver, and are one of the research directions for environmentally friendly alternatives to traditional cyanidation methods. They are also used as auxiliary agents in some mineral processing processes.

8.Analytical Chemical Reagents

Sodium thiocyanate is a classic analytical reagent for detecting ferric ions (forming a blood-red complex) and for argentometric titration (Volhard method), and is widely used in laboratory testing.

9.Industrial auxiliaries such as those used in printing and dyeing, and rubber production.

Sodium thiocyanate can also be used as a dyeing and printing auxiliary agent, a rubber treatment auxiliary agent, and a color film developing agent (historical use). With its characteristics of “easy solubility, stability and good coordination ability”, it has found application scenarios in many industries.

Summarize

Sodium thiocyanate (NaSCN, CAS No. 540-72-7) is a white, highly hygroscopic, and readily soluble inorganic thiocyanate. Its SCN⁻ ions exhibit halogen-like properties and strong coordination ability, enabling them to undergo characteristic reactions with metal ions such as iron and silver. Industrial-grade sodium thiocyanate typically focuses on indicators such as main content, moisture content, iron content, chloride/sulfate ratio, and water-insoluble matter.

Due to its easy solubility and strong coordination properties, sodium thiocyanate is widely used as an early-strength agent and antifreeze agent for concrete, a solvent for acrylic fiber spinning, an additive for electroplating and electroless plating, and an important industrial raw material in fields such as pesticides, oil fields, precious metal extraction, and analytical chemistry. Although ordinary consumers do not come into direct contact with its pure form, they may encounter it in the industrial chain from buildings under construction in winter, acrylic sweaters worn on their bodies, and home hardware and bathroom fixtures.