GLYCERIN (GLYCEROL, E422)

1. Chemical Identity and Material Classification

Chemical Name: Propane-1,2,3-triol, Glycerol, Glycerin
Synonyms: Glycyl Alcohol, Propanetriol, 1,2,3-Trihydroxypropane, Trihydroxypropane, 1,2,3-Propanetriol
CAS Number: 56-81-5
EC Number (EINECS): 200-289-5
Molecular Formula: C₃H₈O₃
Molecular Weight: 92.09 g/mol
Chemical Class: Sugar alcohol (polyol), trihydric alcohol
HS Code / GTIP: 1520.00.00 (crude); 2905.45.00 (refined)
E Number: E422 (food additive)
REACH Status: Registered under EC 200-289-5

2. Physical Properties

2.1 General Physical Properties

Property	Value
Appearance (20°C)	Colorless, odorless, clear, viscous hygroscopic liquid
Physical state (20°C)	Liquid (viscous)
Odor	Odorless
Taste	Sweet (approximately 0.6× sweetness of sucrose)
Density (20°C)	1.261 g/cm³ (1.26–1.26 g/cm³)
Specific gravity (20°C)	1.26
Refractive index (nD20)	1.472–1.474
Viscosity (20°C)	1,412 cP (1.412 Pa·s) – very viscous
Viscosity (40°C)	300 cP
Melting point / Freezing point	17.8°C (64°F) (supercools; may remain liquid below this temperature)
Boiling point (at 760 mmHg)	290°C (554°F) (decomposes)
Boiling point (at 20 mmHg)	130–140°C
Flash point	160°C (closed cup) – combustible
Autoignition temperature	370°C (698°F)
Vapor pressure (20°C)	<1 mmHg (very low)
Vapor density (air = 1)	3.17 (heavier than air)
Surface tension (20°C)	63.4 mN/m
Heat of vaporization	86.7 kJ/mol

2.2 Thermal Properties

Parameter	Value
Specific heat capacity (20°C)	2.41 kJ/(kg·K) (0.576 cal/g·°C)
Thermal conductivity (20°C)	0.29 W/(m·K)
Coefficient of thermal expansion (20°C)	0.00061 /K
Heat of fusion	18.3 kJ/mol
Decomposition temperature	>200°C (produces acrolein – irritating)

2.3 Freezing / Crystallization Behavior

Parameter	Value
Freezing point (pure)	17.8°C (64°F)
Supercooling	Glycerin readily supercools – may remain liquid below freezing point
Crystallization	Slow; can be induced by seeding

Note: 99.5% glycerin may crystallize at temperatures between 12–17°C. Warming to 25–30°C with mild agitation will re-dissolve crystals without affecting quality.

3. Solubility

3.1 Solvent Solubility

Solvent	Solubility
Water	Completely miscible (all proportions)
Ethanol (95%)	Completely miscible
Methanol	Completely miscible
Acetone	Sparingly soluble
Propylene glycol	Completely miscible
Polyethylene glycol	Completely miscible
Diethyl ether	Sparingly soluble
Chloroform	Insoluble
Benzene	Insoluble
Carbon tetrachloride	Insoluble
Oils (mineral, vegetable)	Slightly soluble (acts as humectant, not solvent)

3.2 Solution Properties

Parameter	Value
pH (10% solution, 20°C)	5.5–7.0 (neutral to slightly acidic)
pH (50% solution, 20°C)	5.0–6.5
Heat of dilution (in water)	Exothermic (heats up)

4. Chemical Properties

4.1 Molecular Structure

Structure: HOCH₂–CH(OH)–CH₂OH

Three hydroxyl groups (one secondary, two primary)
Trihydric alcohol (three -OH groups)
High hydroxyl density – responsible for hygroscopicity and hydrogen bonding
Chiral center (optically inactive; glycerol is not chiral due to symmetry)

4.2 Key Chemical Characteristics

Parameter	Value
Number of hydroxyl groups	3
Hydroxyl groups	Two primary (C1, C3), one secondary (C2)
pKa (25°C)	14.15 (very weak acid)
Isoelectric point	Not applicable (no ionizable groups)
Refractive index (nD20)	1.472–1.474

4.3 Chemical Reactivity

Reaction Type	Description
Esterification	With fatty acids → mono-, di-, triglycerides (fats and oils)
Transesterification	With methanol → biodiesel (fatty acid methyl esters) + glycerin (by-product)
Etherification	With alcohols → glycerol ethers
Acetal / ketal formation	With aldehydes/ketones → solketal
Dehydration	Heating with KHSO₄ or H₂SO₄ → acrolein (unsaturated aldehyde, toxic)
Oxidation	With strong oxidizers → glyceraldehyde, dihydroxyacetone, tartronic acid, mesoxalic acid
Chlorination	With HCl → chlorohydrins (epichlorohydrin precursor)
Nitration	With nitric acid → nitroglycerin (explosive)

4.4 Hygroscopicity

Relative Humidity	Equilibrium Moisture Content (%)
0% RH	~0%
20% RH	~10%
50% RH	~25%
80% RH	~45%

Key property: Glycerin attracts and retains moisture from the air – excellent humectant.

4.5 Thermal Decomposition

Temperature	Products
>200°C	Decomposes to acrolein (toxic, irritating aldehyde), acetaldehyde, formaldehyde, carbon monoxide
>290°C	Boiling with decomposition
Combustion	CO₂, H₂O, acrolein (incomplete combustion)

4.6 Incompatibilities

Substance	Hazard
Strong oxidizing agents (HNO₃, H₂O₂, KMnO₄, chromates)	Fire/explosion risk, oxidation
Strong acids (H₂SO₄, H₃PO₄, HCl)	Dehydration to acrolein (toxic)
Strong bases	May cause degradation at high temperatures
Nitrating mixtures	Forms nitroglycerin (highly explosive)

5. Quality Specifications

5.1 Glycerin Grades – Overview

Grade	Purity	Primary Use
Technical Grade	85–99%	Industrial applications (antifreeze, lubricants, textiles)
Cosmetic Grade	99.5–99.7%	Personal care (lotions, creams, soaps, shampoos)
Pharmaceutical Grade (USP/EP)	99.5–101.0%	Pharmaceuticals (syrups, suppositories, topical preparations)
Food Grade (E422)	99.5–99.9%	Food and beverage applications (humectant, sweetener, solvent)
Biodiesel Grade	80–85%	Crude by-product from biodiesel production

5.2 Pharmaceutical Grade (USP / Ph. Eur.)

Parameter	Specification	Test Method
Assay (anhydrous basis)	99.5–101.0%	Titration
Specific gravity (20°C)	1.2607–1.2615	Hydrometer
Refractive index (nD20)	1.471–1.474	Refractometer
Water content (K. Fischer)	≤ 1.0%	Karl Fischer
Residue on ignition	≤ 0.02%	Ignition (800°C)
Chlorides (Cl)	≤ 0.001%	Turbidimetric
Sulfates (SO₄)	≤ 0.002%	Turbidimetric
Heavy metals (as Pb)	≤ 5 ppm	Colorimetric / ICP
Iron (Fe)	≤ 5 ppm	Colorimetric
Arsenic (As)	≤ 1 ppm	Atomic absorption
Lead (Pb)	≤ 1 ppm	Atomic absorption
Reducing substances	Passes test	Redox titration
Fatty acids and esters	≤ 0.1% (as butyric acid)	Titration
Glucose	Passes test (no coloration)	Colorimetric
Acrolein	Passes test (no yellow coloration)	Colorimetric
Bacterial endotoxins	≤ 10 IU/g	LAL test

5.3 Food Grade (E422)

Parameter	Specification
Purity (anhydrous basis)	99.5–99.9%
Water content	≤ 1.0%
Residue on ignition	≤ 0.02%
Chlorides (Cl)	≤ 0.001%
Sulfates (SO₄)	≤ 0.002%
Heavy metals (as Pb)	≤ 5 ppm
Lead (Pb)	≤ 1 ppm
Arsenic (As)	≤ 1 ppm
Mercury (Hg)	≤ 1 ppm
Cadmium (Cd)	≤ 1 ppm
Reducing substances	Passes test
Fatty acids and esters	≤ 0.1% (as butyric acid)
Color (APHA)	≤ 10

5.4 Cosmetic Grade

Parameter	Specification
Purity	99.5–99.7%
Water content	≤ 1.0%
Glycerin content	≥ 99.5%
Heavy metals	≤ 5 ppm
Ash content	≤ 0.02%
Chlorides	≤ 0.001%
Sulfates	≤ 0.002%
Color (APHA)	≤ 15

6. Production Methods

6.1 Natural / Vegetable Glycerin (Most Common)

Source: Vegetable oils (palm, soybean, canola, sunflower, coconut)

Process (Saponification):

Triglycerides + NaOH → Glycerin + Soap
Crude glycerin recovered from soap lye
Purification: evaporation, distillation, activated carbon treatment, ion exchange
Concentration to 99.5%+

Process (Transesterification – Biodiesel Co-product):

Triglycerides + Methanol + Catalyst (KOH/NaOH) → Methyl esters (biodiesel) + Glycerin
Crude glycerin (~80%) separated
Purification: acidulation, filtration, distillation, activated carbon, ion exchange
Concentration to 99.5%+

6.2 Synthetic Glycerin

Source: Propylene (petrochemical)

Process:

Propylene → allyl chloride → epichlorohydrin → glycerin
Propylene → acrolein → glycerin

Quality: Equivalent to natural glycerin; pharmaceutical and food grades available

6.3 Crude Glycerin (Biodiesel By-product)

Parameter	Typical Value
Glycerin content	80–85%
Water	10–15%
Methanol	1–5%
Ash (salts)	5–10%
MONG (Matter Organic Non-Glycerol)	2–5%

7. Industrial Applications

7.1 Food and Beverage Industry (E422) – Largest Application

Application	Function	Typical Concentration
Humectant in baked goods	Prevents drying, extends shelf life	0.5–5%
Sweetener in sugar-free products	Low-calorie sweetener (0.6× sucrose)	1–20%
Solvent for flavors and colors	Carrier for extracts, colors	0.1–10%
Plasticizer in edible films	Improves flexibility of food coatings	0.5–5%
Frozen desserts	Prevents ice crystal formation	0.5–3%
Marshmallows and confections	Retains moisture, prevents stickiness	1–10%
Beverages	Body and mouthfeel enhancer	0.1–1%
Processed meats	Moisture retention	0.5–3%
Chewing gum	Plasticizer, humectant	1–5%

Food additive status: E422 – permitted worldwide as GRAS (FDA) and EFSA

7.2 Pharmaceutical Applications

Application	Function	Typical Concentration
Cough syrups	Solvent, sweetener, viscosity modifier	10–40%
Elixirs	Solvent for active ingredients	10–50%
Suppositories	Base (with gelatin)	10–70%
Topical creams and ointments	Humectant, emollient, skin protectant	5–20%
Toothpaste	Humectant, prevents drying	10–30%
Glycerin suppositories	Laxative (irritant effect)	70–90%
Liquid formulations	Sweetener, viscosity enhancer	10–50%
Mouthwash	Sweetener, solvent	5–20%
Otic preparations (ear drops)	Vehicle, emollient	5–50%

7.3 Cosmetics and Personal Care Applications

Application	Function	Typical Concentration
Skin lotions and creams	Humectant, emollient, skin conditioning	1–10%
Shampoos	Humectant, viscosity modifier	0.5–5%
Conditioners	Humectant, antistatic	0.5–3%
Soaps	Moisture retention, clarity	1–10%
Shaving creams	Lubricant, humectant	1–5%
Facial cleansers	Humectant, mildness	1–5%
Deodorants	Humectant, skin conditioning	0.5–2%
Sunscreens	Humectant, solvent	1–5%
Lip balms	Emollient, humectant	1–10%
Baby wipes	Humectant	0.5–2%

INCI Name: Glycerin

7.4 Industrial and Technical Applications

Application	Function	Typical Concentration
Antifreeze	Lowers freezing point (cryoprotectant)	20–50%
De-icing fluids	Aircraft and runway de-icing	10–80%
Textile lubricants	Fiber lubricant, softening agent	1–10%
Printing inks	Humectant, prevents drying on press	1–10%
Paper coatings	Plasticizer, humectant	1–5%
Cellophane production	Plasticizer	5–15%
Explosives manufacturing	Nitroglycerin production	Precursor
Polyurethane foams	Polyol component (alkoxylated)	1–10%
Metalworking fluids	Lubricant, corrosion inhibitor	1–5%
Hydraulic fluids	Base fluid (with water)	10–90%
Tobacco products	Humectant (prevents drying)	1–10%

7.5 Chemical Intermediate

Application	Product
Epichlorohydrin production	ECH (via glycerin-to-ECH process)
Acrolein production	Dehydration
Glycidol production	Dehydration
Propylene glycol production	Hydrogenolysis
Glycerol carbonate	Phosgene-free carbonate synthesis
1,3-Propanediol (PDO)	Fermentation route
Polyglycerol esters	Emulsifiers (E475)

7.6 Bioplastics and Biorefinery

Application	Description
Polyglycerol	Polymerization → polyglycerols (emulsifiers, lubricants)
Propylene glycol	Hydrogenolysis
Acrylic acid	Dehydration + oxidation
Lactic acid	Fermentation
Succinic acid	Fermentation

8. Toxicology and Safety

8.1 Acute Toxicity

Parameter	Value	Classification
Oral LD₅₀ (rat)	12,600–40,000 mg/kg (very low toxicity)	Not classified
Dermal LD₅₀ (rabbit)	>10,000 mg/kg	Not classified
Inhalation LC₅₀	Not determined (low vapor pressure)	Not classified
Skin irritation	Non-irritant (generally)	Not classified
Eye irritation	Mild irritant (may cause mild redness)	Not classified
Skin sensitization	Non-sensitizer	Not classified

8.2 Chronic Toxicity

Endpoint	Classification
Carcinogenicity	Not classified (IARC Group 3 – not classifiable)
Mutagenicity	Negative
Reproductive toxicity	Not classified
Target organ toxicity	Not classified (low toxicity)

8.3 GHS Classification

Classification	Category
Signal word	None (not classified as hazardous)
Hazard statements	None (under normal conditions)
Precautionary statements	P264, P280 (for industrial handling – eye protection)

8.4 Special Hazards (Decomposition)

Hazard	Description
Acrolein formation	Glycerin heated to >200°C with dehydration agents (H₂SO₄, KHSO₄) produces acrolein – toxic, flammable, lachrymatory
Combustion	Produces CO, CO₂, acrolein, smoke

9. Safety Precautions and Personal Protective Equipment (PPE)

Hazards:
- Very low acute toxicity
- May cause mild eye irritation (dust/mist)
- Hygroscopic – absorbs moisture from air
- Combustible (flash point 160°C)
- When heated to decomposition (>200°C), produces toxic acrolein
PPE (recommended – industrial handling):
- Safety glasses (EN 166) – side shields (for splash protection)
- Chemical-resistant gloves (nitrile – optional, low hazard)
- Protective clothing (for bulk handling)
- Respiratory protection: Not normally required (low vapor pressure)
Engineering controls:
- Adequate ventilation
- Eyewash stations
First aid:
- Inhalation: Move to fresh air
- Skin contact: Wash with soap and water
- Eye contact: Rinse with water for 15 minutes
- Ingestion: Rinse mouth; drink water (low hazard)

10. Environmental Fate

Parameter	Value
Biodegradability	Readily biodegradable (OECD 301) – 100% degradation
Aquatic toxicity (fish, LC₅₀, 96 hours)	>10,000 mg/L (very low toxicity)
Daphnia magna (EC₅₀, 48 hours)	>5,000 mg/L
Algal toxicity (EC₅₀, 72 hours)	>1,000 mg/L
Bioaccumulation	Very low (BCF <10)
Mobility in soil	High (high water solubility)
WGK Germany	1 (low hazard to water)
Disposal method	Incineration (CO₂ + H₂O) or wastewater treatment (biodegradable)

11. Storage and Shelf Life

11.1 Storage Conditions

Parameter	Requirement
Storage temperature	15–30°C (room temperature)
Prevent from	Freezing (may crystallize; warm to 25–30°C to re-dissolve), moisture (hygroscopic – keep tightly sealed)
Container	Keep tightly closed in original container (HDPE, stainless steel, glass, aluminum, lined steel)
Protect from	Strong oxidizing agents, strong acids (dehydration to acrolein)
Environment	Cool, dry, well-ventilated area
Shelf life (sealed)	24–36 months
Shelf life (opened)	12–24 months (if kept dry and sealed)

11.2 Container Materials

Container Type	Suitability
HDPE (High-Density Polyethylene)	Suitable
Polypropylene	Suitable
Stainless steel (304, 316)	Suitable
Glass	Suitable
Aluminum	Suitable
Lined carbon steel	Suitable
Unlined carbon steel	Not recommended (may cause discoloration)

12. Transport Information

Regulation	Classification
UN Number	Not regulated (non-hazardous)
ADR/RID	Not classified as dangerous goods
IMDG	Not regulated
IATA	Not regulated
Proper shipping name	Glycerin, Glycerol (non-hazardous)

13. Synonyms and Common Names

English: Glycerin, Glycerol, Glycerine, Glycyl Alcohol, Propanetriol, 1,2,3-Propanetriol, 1,2,3-Trihydroxypropane, Glyceritol
Trade names: Glycerine 99.5%, Glycerol USP, Glycerol Ph. Eur., Vegetable Glycerin, Synthetic Glycerin
French: Glycérine
German: Glycerin
Spanish: Glicerina
Turkish: Gliserin, Gliserol

14. Regulatory Status

Regulation	Status
REACH (EU)	Registered (EC 200-289-5)
TSCA (US)	Listed
FDA	GRAS (Generally Recognized as Safe) – food additive E422
EFSA	Permitted as food additive (E422)
USP / Ph. Eur.	Monographed
EPA	Not restricted

15. Why Choose Glycerin?

Advantage	Description
Excellent humectant	Attracts and retains moisture – ideal for cosmetics, foods, and pharmaceuticals
Very low toxicity	Oral LD₅₀ >12,600 mg/kg – safe for food, pharmaceutical, and cosmetic use
Versatile	Used in foods, cosmetics, pharmaceuticals, industrial applications
Biodegradable	100% biodegradable – environmentally friendly
Sweet taste	Natural sweetener (0.6× sucrose) – suitable for sugar-free formulations
Compatible with many ingredients	Miscible with water, alcohols, glycols
FDA and EFSA approved	GRAS for food use (E422)
Multiple grades available	Technical, cosmetic, pharmaceutical, food grades
Renewable source (vegetable glycerin)	Derived from vegetable oils (palm, soybean, coconut)
Good solvent	Solubilizes many active ingredients

Limitations:

High viscosity (1,412 cP at 20°C) – Requires pumping consideration; may need warming for easy transfer
Hygroscopic – Absorbs moisture; requires airtight storage
Crystallizes below 17.8°C – May solidify in cold storage; requires warming before use
Combustible – Flash point 160°C; keep away from ignition sources
Forms acrolein upon thermal decomposition – Toxic; avoid overheating (>200°C) with dehydration agents

16. Glycerin Grades – Comparison Table

Parameter	Technical Grade	Cosmetic Grade	Pharmaceutical Grade (USP/EP)	Food Grade (E422)	Biodiesel Grade (Crude)
Purity	85–99%	99.5–99.7%	99.5–101.0%	99.5–99.9%	80–85%
Water content	≤2–5%	≤1.0%	≤1.0%	≤1.0%	10–15%
Ash content	≤0.1–0.5%	≤0.02%	≤0.02%	≤0.02%	5–10%
Heavy metals	≤10–50 ppm	≤5 ppm	≤5 ppm	≤5 ppm	>50 ppm
Color (APHA)	≤30–50	≤15	≤10	≤10	Dark
Applications	Industrial, antifreeze	Cosmetics, personal care	Pharmaceuticals, medical	Food, beverages	Biodiesel co-product

17. Glycerin vs. Other Polyols – Comparison

Property	Glycerin (C3)	Propylene Glycol (C3)	Sorbitol (C6)	Ethylene Glycol (C2)
Formula	C₃H₈O₃	C₃H₈O₂	C₆H₁₄O₆	C₂H₆O₂
OH groups	3	2	6	2
Viscosity (20°C)	1,412 cP	56 cP	Very high (syrup)	21 cP
Sweetness	0.6× sucrose	0.5× sucrose	0.6× sucrose	Sweet (toxic)
Toxicity	Very low	Low	Very low	High (toxic)
Humectancy	Excellent	Good	Excellent	Good
Freezing point	17.8°C	-59°C	95–99°C (solid)	-13°C
Primary use	Food, cosmetic, pharma	Food, cosmetic	Food, toothpaste	Antifreeze
Biodegradability	Yes	Yes	Yes	Yes

18. Frequently Asked Questions (FAQs)

Q1: What is the difference between glycerin and glycerol?
A1: Glycerin and glycerol are the same compound (C₃H₈O₃). "Glycerin" is the common name (often used for commercial grades), while "Glycerol" is the chemical name (IUPAC).

Q2: Is glycerin safe to eat?
A2: Yes, food-grade glycerin (E422) is GRAS (Generally Recognized as Safe) by FDA and EFSA. It is used as a humectant, sweetener, and solvent in many food products.

Q3: Is glycerin vegan?
A3: Glycerin can be derived from vegetable oils (palm, soybean, coconut) – vegetable glycerin is vegan. It can also be derived from animal fats (tallow) – not vegan. Synthetic glycerin (from propylene) is vegan.

Q4: Why does glycerin crystallize in cold storage?
A4: Pure glycerin has a freezing point of 17.8°C (64°F). Below this temperature, it crystallizes. Warming to 25–30°C with mild agitation will re-dissolve crystals without affecting quality.

Q5: How is glycerin used in biodiesel production?
A5: Glycerin is a co-product of biodiesel production (transesterification). For every 100 kg of biodiesel produced, approximately 10 kg of crude glycerin is generated.

19. Storage Recommendations

Condition	Recommendation
Winter storage	Store in heated warehouse (20–30°C) to prevent crystallization
Bulk storage	Use tank heating or circulation to maintain liquid state
Containers	HDPE, stainless steel, aluminum, lined steel
Incompatibles	Strong oxidizing agents, strong acids
Hygroscopicity	Keep containers tightly sealed; use nitrogen blanketing for long-term storage
Shelf life	24–36 months (unopened); 12–24 months (opened, if kept dry)

20. Summary Table – Key Specifications at a Glance

Parameter	Value
Product Name	Glycerin (Glycerol, E422)
CAS Number	56-81-5
Molecular Formula	C₃H₈O₃
Molecular Weight	92.09 g/mol
Appearance	Colorless, odorless, clear, viscous liquid
Density (20°C)	1.261 g/cm³
Viscosity (20°C)	1,412 cP
Refractive Index (nD20)	1.472–1.474
pH (10% solution)	5.5–7.0 (neutral)
Melting Point	17.8°C (64°F)
Boiling Point	290°C (554°F)
Flash Point	160°C
Water Solubility	Completely miscible
log P	-1.76
Assay (USP/Ph. Eur.)	99.5–101.0%
Primary Applications	Food (E422), cosmetics (humectant), pharmaceuticals (syrups, suppositories), industrial (antifreeze, lubricants), chemical intermediate
Oral LD₅₀ (rat)	12,600–40,000 mg/kg (very low toxicity)
GHS Signal Word	None (non-hazardous)
Hazard Statements	None
Biodegradability	Readily biodegradable (100%)
UN Number	Not regulated

This TDS is prepared in compliance with ISO 11014-1 format and is intended for food technologists, cosmetic formulators, pharmaceutical scientists, chemical engineers, and procurement professionals. Certificates of Analysis (CoA), Safety Data Sheets (SDS), and sample validation reports are available upon request.

Glycerin, Glycerol, Glycyl Alcohol, Propanetriol, E422, 56-81-5