RED PHOSPHORUS

Red phosphorus is an industrially important phosphorus allotrope recognized for its solid-state stability and distinctive reddish appearance.
Red phosphorus serves as a functional raw material in flame-resistant polymers, match compositions, specialty chemicals, and advanced material technologies.
Compared with more reactive phosphorus forms, Red phosphorus offers easier handling and broader suitability for controlled industrial processing.

CAS Number: 7723-14-0
EC Number: 231-768-7
Molecular Formula: P
Molecular Weight: 30.97 g/mol

Synonyms: Red phosphorus, Phosphorus Red, Red Elemental Phosphorus, Amorphous Red phosphorus, Amorphous Phosphorus, Phosphorus, Red, Elemental Phosphorus, Red Form, Red Phosphorous Material, Polymeric Phosphorus, Noncrystalline Red phosphorus, Red phosphorus Powder, Red phosphorus Allotrope, Phosphorus (Red Modification), Phosphorus, Amorphous Red, Red P

Red phosphorus is a stable allotrope of elemental phosphorus that appears as a dark red to reddish-brown amorphous or microcrystalline solid.
Red phosphorus is less reactive and less volatile than white phosphorus and is widely used in flame-retardant formulations, pyrotechnic compositions, safety matches, semiconductor-related applications, and certain chemical synthesis processes.
Red phosphorus's thermal stability, low vapor pressure, and phosphorus-rich composition make it valuable in industrial materials where controlled reactivity and flame-inhibiting performance are required.

Red phosphorus is the common name of several forms of elemental phosphorus, often considered one of its allotropes.
Red phosphorus's most common shape is an amorphous polymeric red solid that is stable in air.

Amorphous Red phosphorus is easily obtained when exposing white phosphorus to sunlight or heating, which was discovered in 1847 by Anton von Schrötter.
When sublimed in a vacuum, amorphous Red phosphorus can transform into a crystalline form, known either as violet or Hittorf's phosphorus, after the name of its discoverer.
When this process is carried out in the presence of iodine, another crystalline is obtained alongside it, called fibrous Red phosphorus.

Applications of amorphous Red phosphorus include matches and fire retardants.

Red phosphorus is the most common allotrope of phosphorus due to its relative stability compared to white phosphorus.
Red phosphorus has a variety of uses including, but not limited to, use as a catalyst, battery anode, flame retardant, and igniter.

Chemical formula P is composed of phosphorous, white, black and red.
There are 10 allotropes (separate form) collected in three main groups.

Red phosphorus consists of white phosphorus with sun light and heat effect.
Unlike white phosphorus, Red phosphorus is not easily ignited, does not glow and is not toxic.

Red phosphorus's melting temperature is much higher.
Red phosphorus is stable in the air.

The structure of Red phosphorus is very complex and has not been fully explained.
Phosphorus atoms can be said to be in the form of infinite chains.

White phosphorus P4 is called Red phosphorus P8.
Red phosphorus is less active than white phosphorus but it can give the same reaction products as white phosphorus.

Red phosphorus is defined as a polymeric and thermally stable allotropic form of phosphorus, effective as a flame-retardant additive in polymers, particularly at concentrations below 10%.
Red phosphorus is relatively nontoxic and acts by quenching free radicals and reducing heat production during combustion, although it can react with moisture to produce toxic phosphine gas.

Red phosphorus is a stable allotrope of elemental phosphorus, supplied as a deep red, amorphous powder.
Red phosphorus is less reactive than white phosphorus and is widely used in pyrotechnics, safety applications, and chemical synthesis due to its controlled reactivity and thermal stability.

Amorphous Red phosphorus:
Amorphous Red phosphorus chain fragments, with (top) or without (bottom) interchain connection
Amorphous Red phosphorus is polymeric in structure and therefore insoluble in most solvents.
Red phosphorus is easily obtained by irradiation or heating of white phosphorus.

The standard enthalpy of formation of amorphous Red phosphorus is −17.6 kJ/mol.
Red phosphorus is the most kinetically stable form of phosphorus.

Because of this, Red phosphorus does not exhibit the intense and comprehensive reactivity of white phosphorus.
And is much more stable under standard conditions.
However, Red phosphorus is less stable than black phosphorus, the most thermodynamically stable allotrope of phosphorus.

Because of its polymeric structure, amorphous Red phosphorus is insoluble in most solvents.
Red phosphorus also shows semiconductor properties.

Crystalline Red phosphorus:

Violet or Hittorf's phosphorus:
Hittorf's phosphorus, or violet phosphorus, is one of the crystalline forms of Red phosphorus.

Violet phosphorus can be prepared by sublimation of Red phosphorus in a vacuum, in the presence of an iodine catalyst.

Red phosphorus is chemically similar to Red phosphorus.
There are, however, subtle differences.

Violet phosphorus ignites upon impact in air, while Red phosphorus is impact stable.
Violet phosphorus doesn't ignite in the presence of air upon room temperature contact with bromine, unlike Red phosphorus.
The reaction of Red phosphorus and bromine alone does not generate a flame.

Fibrous Red phosphorus:
Fibrous Red phosphorus is another crystalline form of Red phosphorus.
Red phosphorus is obtained along with violet phosphorus when Red phosphorus is sublimed in a vacuum in the presence of iodine.

Red phosphorus is structurally similar to violet phosphorus.
However, in fibrous Red phosphorus, phosphorus chains lie parallel instead of orthogonal, unlike violet phosphorus.
Fibrous Red phosphorus, similar to Red phosphorus, displays activity as a photocatalyst.

Applications of Red Phosphorus:
Red phosphorus is widely used as a flame-retardant additive in polymers, engineering plastics, electrical components, and protective materials.
Red phosphorus is used in the manufacture of safety matches, particularly in the striking surface, where controlled ignition is required.

Red phosphorus also serves as an intermediate in the production of various phosphorus-containing chemicals, including phosphides and specialty phosphorus compounds.
In the electronics and semiconductor industries, high-purity grades may be used as a phosphorus source for specialized material-processing applications.

Red phosphorus is also incorporated into certain metallurgical, ceramic, and specialty material formulations to modify chemical or thermal performance.
Due to its relatively low volatility and greater stability compared with white phosphorus, Red phosphorus is preferred in many industrial applications requiring a solid elemental phosphorus source.

Flame retardants:
Amorphous Red phosphorus can be used as a very effective flame retardant, especially in thermoplastics (e.g. polyamide) and thermosets (e.g. epoxy resins or polyurethanes).
The flame retarding effect is based on the formation of polyphosphoric acid.

Together with the organic polymer material, these acids create a char which prevents flame propagation.
The safety risks associated with phosphine generation and friction sensitivity of Red phosphorus can be effectively minimized by stabilization and micro-encapsulation.
For easier handling, Red phosphorus is often used in form of dispersions or masterbatches in various carrier systems.

However, for electronic/electrical systems, Red phosphorus flame retardant has been effectively banned by major OEMs due to its tendency to induce premature failures.
One persistent problem is that Red phosphorus in epoxy molding compounds induces elevated leakage current in semiconductor devices.
Another problem was acceleration of hydrolysis reactions in PBT insulating material.

Red phosphorus can be used as a:
Photocatalyst for the formation of H2 from water.
Catalyst in the synthesis of tris(2-pyridyl)phosphine by reacting with 2-bromopyridine in the presence of a base.

Flame retardant along with aluminum oxide in recycled poly(ethylene terephthalate).
Anode material in combination with carbon composites for sodium-ion batteries.

Safety matches:
Red phosphorus is used, along with abrasives, on the strike pads of modern matches.
Red phosphorus's discovery allowed for the development of safer matches (historically called safety matches), as well as much less hazardous manufacturing.

The match head, containing potassium chlorate, will ignite upon friction with the strike pad.
However, the red color of the matchhead is due to addition of red iron oxide, and has nothing to do with phosphorus.

Chemical synthesis:
Amorphous Red phosphorus reacts with bromine and iodine to form phosphorus tribromide and phosphorus triiodide.
Both are useful as halogenating agents, for example in replacing the hydroxyl group of alcohols.

Phosphorus triiodide can also be used to produce hydroiodic acid after hydrolysis.
This reaction is notable in the illicit production of methamphetamine and Krokodil, where hydrogen iodide acts as a reducing agent.

Red phosphorus is often used to prepare chemicals where the P-P bond is retained.
Upon room temperature reaction with sodium chlorite, Na2H2P2O6 is formed.

Red phosphorus can be used as an elemental photocatalyst for hydrogen formation from water.
Red phosphorus displays a steady hydrogen evolution rates of 633 μmol/(h⋅g) by the formation of small-sized fibrous phosphorus.
Red phosphorus has also been researched as a sodium ion battery anode.

Production and Reactions of Red Phosphorus:
Red phosphorus is obtained by reducing the phosphate rocks with SiO2 by coke in electric furnaces.

2Ca3 (PO4) 2 SiO2 10Ca ---> P4 6CaSiO4

During this reaction, the P4 molecules pass into the gas phase.

Cooled with water and concentrated to white phosphorus:
2Ca3 (PO4) 2 6SiO2 x 6CaSiO3 P4O10 ---> P4O10 10C à 10CO P

Reduced phosphorus can be produced by heating this obtained P4 chemical to 250-300 ° C for a long time.

Stability and Reactivity of Red Phosphorus:

Chemical Stability:
Stable under recommended storage conditions, but combustible and capable of ignition when exposed to sufficient heat, sparks, or flame.

Reactivity:
May react vigorously with strong oxidizing agents and other incompatible reactive substances.

Conditions to Avoid:
Heat, open flames, sparks, static discharge, friction, dust formation, and contact with incompatible materials.

Incompatible Materials:
Strong oxidizing agents, halogens, and other highly reactive chemicals.

Handling and Storage of Red Phosphorus:

Safe Handling:
Avoid creating or inhaling dust and keep away from heat, sparks, flames, and other ignition sources.
Use appropriate grounding and precautions against static discharge where applicable.

Storage Conditions:
Keep containers tightly closed in a cool, dry, well-ventilated area, separated from ignition sources and incompatible materials.

First Aid Measures of Red Phosphorus:

Inhalation:
Move the affected person to fresh air and obtain medical attention if coughing, irritation, or breathing difficulty persists.

Skin Contact:
Remove contaminated clothing and wash the affected area thoroughly with soap and water.

Eye Contact:
Rinse cautiously with clean water for several minutes and seek medical attention if irritation persists.

Ingestion:
Rinse mouth and obtain medical advice if discomfort or adverse symptoms occur.

Firefighting Measures of Red Phosphorus:

Suitable Extinguishing Media:
Use an extinguishing medium suitable for combustible solids and the surrounding fire; follow the specific product SDS for the supplied grade.

Special Hazards:
Burning Red phosphorus may produce irritating and hazardous phosphorus oxide fumes.

Protective Equipment:
Firefighters should wear full protective clothing and self-contained breathing apparatus.

Accidental Release Measures of Red Phosphorus:

Personal Precautions:
Eliminate ignition sources, avoid generating airborne dust, provide adequate ventilation, and use suitable protective equipment.

Cleanup Methods:
Carefully collect spilled material using non-sparking methods and place it in an appropriate closed container.

Environmental Precautions:
Prevent uncontrolled release to drains, waterways, and the environment.
Red phosphorus is classified by Sigma-Aldrich as harmful to aquatic life with long-lasting effects for the referenced grade.

Exposure Controls/Personal Protective of Red Phosphorus:

Engineering Controls:
Provide adequate general ventilation and local exhaust where dust may be generated.

Eye Protection:
Wear protective safety goggles or suitable eye protection.

Hand Protection:
Use appropriate chemical-resistant protective gloves.

Skin Protection:
Wear protective work clothing and minimize direct skin exposure.

Respiratory Protection:
Use suitable particulate respiratory protection when dust exposure cannot be adequately controlled; Sigma-Aldrich lists particulate respiratory protection, gloves, and eye protection for its Red phosphorus product.

Identifiers of Red Phosphorus:
CAS Number: 7723-14-0
EC Number: 231-768-7
Molecular Formula: P
Molecular Weight: 30.97 g/mol
Allotrope: Red phosphorus
UN Number: 1338

Article No.: 05257
Grade: For Synthesis
Purity: 98%
CAS No.: 7723-14-0
Molecular Formula: P
Molecular Weight: 30.97
H.S. Code: 2804.7020

CAS Number: 7723-14-0
Appearance: powder
Color: Red-Brown
Vapor Density: 4.7 (air = 1)
Water Solubility: Negligible
Molecular Weight: 30.973762
Chemical Name: Red phosphorus
Chemical Formula: P

Empirical Formula (Hill Notation): P
CAS Number: 7723-14-0
Molecular Weight: 30.97
NACRES: NA.22
PubChem Substance ID: 57646724
UNSPSC Code: 12141909
EC Number: 231-768-7
MDL number: MFCD00133771

CAS Number: 7723-14-0
DrugBank: DB14151
EC Number: 231-768-7
PubChem CID: 5462309
UNII: 27YLU75U4W
UN number: 1338
CompTox Dashboard (EPA): DTXSID1024382
InChI: InChI=1S/P
Key: OAICVXFJPJFONN-UHFFFAOYSA-N
SMILES: [P]

Properties of Red Phosphorus:
Appearance: Dark red to reddish-brown solid or powder
Odor: Odorless
Molecular Formula: P
Molecular Weight: 30.97 g/mol

Chemical formula: P
Molar mass: 30.974 g·mol−1
Density: 2.34 g/cm3
Melting point: 590 °C (1,094 °F; 863 K)

Physical state at 20 °C: Solid
Colour: Red powder
Melting point/ Freezing point [°C]: 280 °C
Auto-ignition temperature [°C]: 260°C
Vapour pressure [20°C]: 0.04 hPa at 20 °C
Density [g/cm3]: 2.34
Solubility in water [% weight]: Insoluble in water

vapor density: 0.02 (vs air)
Quality Segment: 100
vapor pressure: 0.03 mmHg ( 21 °C), 1 mmHg ( 76.6 °C)
assay: ≥97.0%
autoignition temp.: 500 °F
resistivity: 10 μΩ-cm, 20°C
mp: 416 °C (subl.) (lit.)
density: 2.34 g/mL at 25 °C (lit.)
cation traces: Fe: ≤2000 mg/kg
storage temp.: room temp
SMILES string: [P]
InChI: 1S/P
InChI key: OAICVXFJPJFONN-UHFFFAOYSA-N

Specifications of Red Phosphorus:
Appearance: Red powder
Assay (as P): Min 98%