Alkalis & Bases — Hazardous Chemicals Safety Reference

⚗️ Class Overview — Alkalis & Bases

Golden rule: Never neutralise an alkali burn with acid — the exothermic reaction deepens the injury. Flush with copious water only.
Alkaline splashes to the eye are a genuine ophthalmic emergency — saponification progresses even after washing, so a mandatory ophthalmology review is needed regardless of apparent recovery.
Sulphide and hypochlorite compounds generate deadly gases (H₂S, Cl₂) if accidentally acidified — pH control and segregated storage from all acids is non-negotiable in ETPs and tanneries.
Reactive metals (aluminium, zinc) evolve hydrogen gas on contact with strong alkalis — never store or transfer in these containers.

📑 Jump to a Chemical

Sodium Hydroxide (NaOH)Potassium Hydroxide (KOH)Aqueous Ammonia / Anhydrous NH₃ Sodium Carbonate (Na₂CO₃)Sodium Hypochlorite (NaOCl)Calcium Hydroxide (Ca(OH)₂)Sodium Bisulphite (NaHSO₃)Sodium Sulphide (Na₂S)Sodium Silicate (Na₂SiO₃)

Sodium Hydroxide (NaOH)

Also known as: Caustic soda / lye

Industrial Uses
Soap, paper, textile mercerising, effluent neutralisation, food

STORAGE HAZARDS

Absorbs CO₂ and moisture; reacts with Al/Zn releasing H₂ — segregate from these metals; keep sealed

HANDLING HAZARDS

Saponifies skin fats causing slippery painless burns; eye splash can cause blindness within seconds

PROCESS HAZARDS

Exothermic dissolution; hot NaOH extremely aggressive to most metals; attacks glass over time

🛡️ Required PPE — Specific Grades & Types

Chemical splash goggles (not just spectacles)
Neoprene or PVC gloves
Face shield for bulk handling
Rubber apron and boots
P2 dust mask for pearl/solid form

🚨 Emergency Procedure — Large Spill / Major Leak

1	Copious water flush — min. 20 min for eyes
2	Do NOT neutralise burns with acid — worsens injury
3	Contain liquid spill; dilute then neutralise with dilute HCl or acetic acid
4	Ophthalmology review for any eye exposure

Potassium Hydroxide (KOH)

Also known as: Caustic potash

Industrial Uses
Soft soap manufacture, batteries (electrolyte), dyes, CO₂ absorption

STORAGE HAZARDS

Strongly hygroscopic; attacks aluminium and zinc; store sealed in PE or SS containers

HANDLING HAZARDS

Similar hazard profile to NaOH; attacks eyes rapidly; concentrated solution causes deep burns

PROCESS HAZARDS

Exothermic dissolution; reacts with many metals generating H₂

🛡️ Required PPE — Specific Grades & Types

Chemical splash goggles
Neoprene gloves
Face shield
Rubber apron

🚨 Emergency Procedure — Large Spill / Major Leak

1	Same protocol as NaOH — copious water flush 20 min
2	Do not neutralise burns with acid
3	Contain spill; dilute generously with water
4	Eye exposure: immediate ophthalmology review

Aqueous Ammonia / Anhydrous NH₃

Also known as: Aqua ammonia / refrigeration ammonia

Industrial Uses
Fertilizer plants, refrigeration, dyes, cleaning agents, cold storage

STORAGE HAZARDS

Anhydrous: PESO licence required above 10 MT; store away from acids, halogens, oxidisers; steel corrodes with moisture

HANDLING HAZARDS

TLV 25 ppm; explosive 15–28% in air; olfactory fatigue a hazard at sustained exposures

PROCESS HAZARDS

Compressor seal failures in refrigeration plants; reacts with Cl₂ to form explosive NCl₃

🛡️ Required PPE — Specific Grades & Types

SCBA for any large spill response
Full chemical splash goggles
Neoprene gloves + chemical suit
NH₃-cartridge APR for low-level work only

🚨 Emergency Procedure — Large Spill / Major Leak

1	Activate site alarm; evacuate upwind
2	SCBA teams shut off valve if safe
3	Water fog to knock down vapour — no solid jet
4	Notify DISH + PESO for anhydrous tonner incident
5	Move victims to fresh air; O₂; call 108

Sodium Carbonate (Na₂CO₃)

Also known as: Soda ash / washing soda

Industrial Uses
Glass, detergents, paper, water treatment, effluent neutralisation

STORAGE HAZARDS

Low acute hazard; hygroscopic; dust generation in bag handling causes respiratory irritation

HANDLING HAZARDS

Mildly alkaline solution irritates skin/eyes; dust irritates respiratory tract; safe at low concentrations

PROCESS HAZARDS

Reacts with acids generating CO₂ pressure; solution at >10% mildly corrosive to aluminium

🛡️ Required PPE — Specific Grades & Types

Safety goggles for dusty operations
Dust mask P1 for bag-tipping
Nitrile gloves

🚨 Emergency Procedure — Large Spill / Major Leak

1	Spill: sweep dry; avoid generating dust
2	Flush skin/eyes with water if irritation
3	No major emergency procedure required for small quantities
4	For large dust cloud: evacuate and ventilate; P2 mask for cleanup

Sodium Hypochlorite (NaOCl)

Also known as: Bleaching liquor / javelle water

Industrial Uses
Textile bleaching, water treatment, ETP disinfection

STORAGE HAZARDS

Decomposes on heating releasing Cl₂; store in cool dark place away from acids and reducing agents; limited shelf life

HANDLING HAZARDS

Mixing with acids generates Cl₂ gas immediately; caustic burns to skin/mucous membranes; corrosive to metals

PROCESS HAZARDS

Acidic dye effluent mixing with hypochlorite generates Cl₂ unexpectedly

🛡️ Required PPE — Specific Grades & Types

Chemical splash goggles
Nitrile gloves
Chlorine gas respirator for confined space
PVC apron

🚨 Emergency Procedure — Large Spill / Major Leak

1	Cl₂ release: evacuate immediately
2	SCBA for responders; water fog to suppress cloud
3	Neutralise acid source; dilute hypochlorite with large water
4	Hospital for any inhalation — delayed pulmonary oedema risk

Calcium Hydroxide (Ca(OH)₂)

Also known as: Slaked lime / hydrated lime

Industrial Uses
Construction, water treatment, effluent neutralisation, leather liming

STORAGE HAZARDS

Hygroscopic; reacts with CO₂; store in bags in dry, ventilated area; limited shelf life after opening

HANDLING HAZARDS

Dust is highly alkaline and irritating to eyes, skin, and respiratory tract; exothermic if wetted suddenly

PROCESS HAZARDS

Exothermic slaking with water; can cause thermal burns if added to hot liquor

🛡️ Required PPE — Specific Grades & Types

Dust goggles for dry handling
P2 dust mask
Nitrile gloves
Face shield for slaking operations

🚨 Emergency Procedure — Large Spill / Major Leak

1	Dust cloud: evacuate and ventilate; P2 masks for cleanup
2	Eye contact: flush 20 min — alkaline burns progress after washing
3	Skin: wash with water 15 min
4	Spill: wet down gently; avoid dust; sweep and bag

Sodium Bisulphite (NaHSO₃)

Also known as: Sodium hydrogen sulphite

Industrial Uses
Textile dye reduction, paper/pulp, food preservation, photography

STORAGE HAZARDS

Releases SO₂ slowly; store sealed in cool ventilated area; segregate from oxidisers and acids

HANDLING HAZARDS

Solution irritates skin, eyes and respiratory tract; mixing with acids generates SO₂ gas immediately

PROCESS HAZARDS

Heating or acidification releases SO₂; reacts violently with strong oxidisers (KMnO₄, Cl₂)

🛡️ Required PPE — Specific Grades & Types

Chemical goggles
Nitrile gloves
SO₂ gas cartridge respirator for enclosed handling
PVC apron

🚨 Emergency Procedure — Large Spill / Major Leak

1	SO₂ release: evacuate; TLV 2 ppm STEL
2	SCBA for responders; water fog to absorb SO₂
3	Neutralise acid causing SO₂ generation
4	Skin/eye flush 15 min; respiratory: fresh air + hospital

Sodium Sulphide (Na₂S)

Also known as: Stinky soda / sodium sulfide

Industrial Uses
Leather depilation, dyes (sulphur dyes), paper pulp, ore flotation

STORAGE HAZARDS

Releases H₂S on exposure to moisture and CO₂; store sealed in airtight drums; strong reducing agent — keep from oxidisers

HANDLING HAZARDS

H₂S generation in tannery pits/vessels is major hazard; solution burns skin; toxic systemic sulfide ion absorption

PROCESS HAZARDS

pH drop in processing vessel can generate H₂S cloud rapidly; incompatible with acids at any concentration

🛡️ Required PPE — Specific Grades & Types

SCBA for pit/vessel work
Chemical splash goggles
Neoprene gloves
H₂S personal gas monitor — mandatory
Chemical suit

🚨 Emergency Procedure — Large Spill / Major Leak

1	H₂S release: do NOT enter without SCBA
2	Drag victim from outside with lifeline
3	Notify 108; CPR if needed; O₂ therapy
4	Ventilate confined space before any entry
5	Dilute spill with large water only — do not add acid

Sodium Silicate (Na₂SiO₃)

Also known as: Water glass / liquid glass

Industrial Uses
Metal surface cleaning, paper/board coating, detergent, fireproofing, welding electrode coating

STORAGE HAZARDS

Alkaline solution; store in PE containers; freezes below 0°C causing container rupture

HANDLING HAZARDS

Alkaline pH 11–12; skin/eye irritation; solidifies on skin and is difficult to remove; spray mist irritating

PROCESS HAZARDS

At high temperatures silica fume may be generated; mixing with acid generates silica gel and HCl/H₂SO₄ depending on acid

🛡️ Required PPE — Specific Grades & Types

Chemical splash goggles
Nitrile gloves
Face shield for bulk transfer
PVC apron

🚨 Emergency Procedure — Large Spill / Major Leak

1	Skin: wash with soap and water; soften hardened silicate with warm water
2	Eye: flush 20 min water; medical review
3	Spill: dilute with water; neutralise with dilute acid; no significant emergency