Sodium Chloride (NaCl)

1. Basic Properties 

- Chemical Formula: NaCl  

- Appearance: Colorless cubic crystals or white crystalline powder, highly soluble in water, salty taste.  

- Solubility:  

  - Solubility in water: 36 g/100 mL (20°C), minimally affected by temperature.  

  - Slightly soluble in ethanol.  

- Melting Point: 801°C, Boiling Point: 1413°C (volatilizes at high temperatures).  

- Electrical Conductivity: Non-conductive in solid state; conductive when molten or dissolved in water (due to Na? and Cl? ions).  

2. Natural Occurrence and Preparation

- Natural Sources:  

  - Seawater (approximately 2.8% NaCl), salt lakes, rock salt deposits (e.g., Himalayan pink salt).  

- Industrial Production:  

  - Evaporation Method: Drying or boiling seawater or salt lake water to crystallize.  

  - Mining Method: Crushing and purifying rock salt (via dissolution-recrystallization).  

- Laboratory Preparation:  

  - Neutralization of sodium hydroxide (NaOH) with hydrochloric acid (HCl):  

3. Main Applications  

- Food Industry:  

  - Seasoning (table salt), food preservative (e.g., in cured products).  

  - Essential nutrient (daily intake of 3~5 g required to maintain fluid balance).  

- Industrial Use:  

  - Chlor-alkali Industry: Electrolysis to produce chlorine (Cl?), hydrogen (H?), and sodium hydroxide (NaOH).  

  - De-icing agent (lowers the freezing point of water).  

  - Production of chemical raw materials such as soda ash (Na?CO?) and baking soda (NaHCO?).  

- Medical Applications:  

  - Saline solution (0.9% NaCl, used for intravenous infusion or wound cleaning).  

  - Mouthwash (antibacterial and anti-inflammatory).  

- Others:  

  - Animal feed additive.  

  - Traditional uses (e.g., salting, soap making).  

4. Safety Precautions  

- Toxicity:  

  - Excessive long-term intake (>5~6 g/day) may lead to hypertension or kidney strain.  

  - Acute intake of >1 g/kg may cause hypernatremia.  

- Protection:  

  - Dust may irritate the respiratory tract; wearing a mask is recommended during handling.  

- Environmental Impact:  

  - Excessive use of de-icing salt may contaminate soil and water bodies.