Thiourea, 2-Thiourea, Thiocarbamide, Sulfourea, Isothiourea, Pseudothiourea, TU, 62-56-6

Thiourea, 2-Thiourea, Thiocarbamide, Sulfourea, Isothiourea, Pseudothiourea, TU, 62-56-6

THIOUREA

1. PRODUCT DEFINITION AND CHEMICAL IDENTITY

Warning: Thiourea is classified as a suspected carcinogen (Category 2). Appropriate personal protective equipment must be used, and inhalation of dust must be avoided. This product cannot be used in applications involving contact with food.

2. PHYSICAL AND CHEMICAL PROPERTIES

3. FUNCTIONAL PROPERTIES

• Versatile Chemical Intermediate: Thiourea is a fundamental building block in the synthesis of many organic compounds, including dyes, resins, pharmaceuticals, and pesticides. Its sulfur and nitrogen atoms provide a rich reaction chemistry.

• Metal Complexing Agent: Forms stable complexes with many transition metals such as gold, silver, copper, and platinum. This property plays a critical role in processes like metal extraction, ore flotation, and electroplating.

• Vulcanization Accelerator: In the rubber industry, it accelerates the sulfur vulcanization reaction, increasing crosslinking density and speed.

• Crosslinking Agent: Reacts with formaldehyde and other aldehydes to form crosslinked structures in resin systems (e.g., compression moulding powders).

• Reducing Agent / Developer: Used in classic photography to dissolve silver halides and develop images.

• Protein Precipitant: Used in biochemistry laboratories, together with trichloroacetic acid (TCA), as a protein precipitating agent.

4. ALTERNATIVE NAMES AND SYNONYMS

• Thiourea

• 2-Thiourea

• Thiocarbamide

• Sulfourea

• Isothiourea

• Pseudothiourea

5. TYPICAL SPECIFICATIONS (Industrial Grade)

6. SECTORAL APPLICATIONS AND USAGE RATES

Example Formulations:

• Gold Leaching Solution (Analytical / Metallurgy):

  • Thiourea: 10 g/L

  • Sulfuric acid (concentrated): 5 mL/L (pH ~1.5)

  • Iron (III) sulfate (oxidant): 2 g/L
    Gold dissolves by forming an Au[CS(NH₂)₂]₂⁺ complex with thiourea. This is an alternative method to cyanide leaching.

• Acidic Metal Cleaning Bath (Corrosion Inhibited):

  • Hydrochloric acid (30%): 20%

  • Thiourea (inhibitor): 1.0%

  • Non-ionic surfactant: 0.5%

  • Water: 78.5%
    Thiourea adsorbs onto the metal surface in an acidic environment, slowing corrosion.

• Rubber Vulcanization Formulation (NR/SBR):

  • Natural rubber / SBR: 100 parts

  • Carbon black: 50 parts

  • Zinc oxide: 5 parts

  • Stearic acid: 2 parts

  • Sulfur: 2 parts

  • Thiourea (accelerator): 1.5 parts
    Typical cure temperature 140–160 °C.

7. ALTERNATIVES AND COMPARISON

8. REGULATORY STATUS, SAFETY, AND STORAGE

• GHS Classification (CLP Regulation):

  • Signal Word: Warning

  • Hazard Statements:

    • H302: Harmful if swallowed.

    • H351: Suspected of causing cancer.

    • H411: Toxic to aquatic life with long lasting effects.

  • Precautionary Statements: P201, P202, P264, P270, P273, P280, P301+P312, P308+P313, P391, P501.

• Toxicity:

  • Acute oral toxicity (LD50, rat): ~1,750 mg/kg.

  • Irritating to skin and eyes.

  • Chronic exposure may affect thyroid function and can lead to goitre. Suspected carcinogen (IARC Group 3; EU Category 2).

• Storage:

  • Store in a cool (<30 °C), dry, and well-ventilated area in tightly sealed packaging.

  • Protect from moisture; stability decreases in humid environments.

  • Keep away from strong oxidizers, acids, and heat sources.

  • Store separately from food and feedstuffs.

• Personal Protective Equipment (PPE):

  • Avoid breathing dust; use an appropriate dust mask.

  • Use chemical-resistant gloves (nitrile, neoprene) and safety goggles.

  • Ensure adequate ventilation in the working area.

• Waste Disposal:

  • Must be disposed of by a licensed waste facility in accordance with local regulations.

  • Do not pour into drains or waterways; toxic to aquatic life.

• Packaging: Typically 25 kg kraft bags or plastic woven bags; 500–1000 kg big bags.

9. FREQUENTLY ASKED QUESTIONS

Q1: Are thiourea and thiourea dioxide the same?
No, they are completely different chemicals. Thiourea (CH₄N₂S) is primarily an intermediate, complexing agent, and vulcanization accelerator. Thiourea dioxide (CH₄N₂O₂S) is an oxidized derivative of thiourea and is used as a strong reducing agent.

Q2: How does thiourea dissolve gold?
Under acidic and oxidizing conditions (e.g., sulfuric acid + iron (III) ions), thiourea is oxidized on the gold surface to form formamidine disulfide, while gold dissolves as an Au[CS(NH₂)₂]₂⁺ complex. This is an alternative to cyanide leaching.

Q3: Is it carcinogenic?
Thiourea is classified as a Category 2 carcinogen (H351: Suspected of causing cancer) under the EU CLP regulation. It has been observed to cause thyroid tumours in animal studies. Definitive evidence in humans is limited, but it is treated as a suspected carcinogen and must be used with appropriate safety measures.

Q4: Why does it decompose in a humid environment?
In the presence of moisture, thiourea can slowly hydrolyse and form decomposition products such as ammonia and hydrogen sulfide (H₂S). Additionally, microbial growth in a humid environment can accelerate decomposition. Therefore, storage in a dry and sealed environment is critically important.

Q5: What role does it play in photography?
In classic black-and-white photography, thiourea is used in developing baths to dissolve silver halides and create toning effects. Specifically, in sepia toning processes, it converts metallic silver to silver sulfide, producing brown-warm tones.

10. QUICK REFERENCE TABLE