• Pentaboron nonahydride
Formula B5H9
Description A clear colorless liquid with a pungent odor like sour milk.
Uses Fuel for air breathing engines, propellant.

Registry Numbers and Inventories.
CAS 19624-22-7
EC (EINECS/ELINCS) 243-194-4
RTECS RY8925000
RTECS class Other
UN (DOT) 1380
Merck 12,7237
Beilstein/Gmelin 26757 (G)
US TSCA Listed
Korea ECL Listed

Odor Threshold Odor threshold 2.5 mg/m3
Formula B5H9
Formula mass 63.13
Melting point, C -46.6
Boiling point, C 57
Vapor pressure, mmHg 171
Vapor density (air=1) 2.2
Critical temperature 227
Critical pressure 3.9
Density 0.61 g/cm3 (20 C)
Solubility in water Reacts
Viscosity 0.319 cp at 70 deg f
Surface tension 20.8 g/s2
Heat of vaporization 32.1 kJ/mol
Heat of combustion -4268 kJ/mol

Hazards and Protection.
Storage Keep in a cool, dry, dark location in a tightly sealed container or cylinder. Keep away from incompatible materials, ignition sources and untrained individuals. Secure and label area. Protect containers/cylinders from physical damage.
Handling All chemicals should be considered hazardous. Avoid direct physical contact. Use appropriate, approved safety equipment. Untrained individuals should not handle this chemical or its container. Handling should occur in a chemical fume hood.
Protection Wear appropriate protective gloves, clothing and goggles.
Respirators Wear positive pressure self-contained breathing apparatus (SCBA).
Small spills/leaks Do not use water. Keep sparks, flames, and other sources of ignition away. Keep material out of water sources and sewers. Build dikes to contain flow as necessary. Attempt to stop leak if without undue personnel hazard.
Stability Reactive under confinement.
Incompatibilities Reactions with oxygen are often violently explosive Reacts with ammonia to form a diammoniate.
Decomposition On decomposition, it emits toxic fumes.

Flash Point,C 30
Autoignition, C 35
Upper exp. limit, % 98
Lower exp. limit, % 0.42
Fire fighting Move container from fire area if you can do it without risk. Cool containers that are exposed to flames with water from the side until well after fire is out. For massive fire in cargo area, use unmanned hose holder or monitor nozzles; if this is impossible, withdraw from area and let fire burn. Wear positive pressure breathing apparatus and full protective clothing. Evacuation: if fire becomes uncontrollable or container is exposed to direct flame -- evacuate for a radius of 1,500 feet. If material is leaking (not on fire), downwind evacuation must be considered.If material is on fire or involved in fire, do not extinguish unless flow can be stopped. Do not use water. Extinguish small fires with dry chemical or carbon dioxide. For large fires withdraw and let burn.
Fire potential Extremely Very flammable. Combustion imminent.
Hazards Ignites spontaneously in air. Reacts violently with halogenated extinguishing agents. Boron hydrides present considerable fire and explosion hazard. They undergo explosive reaction with most oxidizing agents, including halogenated hydrocarbons. Fires tend to reignite. On decomposition, it emits toxic fumes and can react vigorously with oxidizing materials. Avoid dimethyl sulfoxide, water, most oxidizing agents (including halogenated hydrocarbons). Avoid direct sunlight and sources of ignition, decomposes very slowly at 302.
Combustion products Toxic gases and vapors (such as boron acids) may be released in a fire involving pentaborane.
NFPA Health 4
  Flammability 4  
  Reactivity 2  

Exposure limit(s) NIOSH REL: TWA 0.005 ppm (0.01 mg/m3) ST 0.015 ppm (0.03 mg/m3) NIOSH IDLH: 1 ppm
Exposure effects Cough, wheezing, rapid breathing, mild elevated blood pressure, or fever may be noted after exposure to the boron hydrides, but pentaborane is generally less active than diborane for effects on respiration. Dizziness, weakness, CNS depression and excitation, hallucinations, and incoordination have been seen. Mental deficits have been produced by acute exposures. Tremors leading to seizures and severe brain injury have been seen in high dose pentaborane intoxication. No data were available to assess the potential effects of exposure to this agent during pregnancy or lactation. <br>In one fatal case of pentaborane poisoning, no mature spermatozoa were seen on day eight after exposure.
   Ingestion Nausea is one of the first symptoms seen. Hypersalivation amd anorexia may occur.
   Inhalation Tightness in the chest, dyspnea, cough and wheezing for 3 to 5 days after exposure to boron hydrides. Diborane is the most active boron hydride for respiratory effects; pentaborane and decaborane have fewer respiratory symptoms.
   Skin Pentaborane can be rapidly fatal by the dermal route. Pentaborane is an irritant of the skin and mucous membranes. Reddened skin may occur from exposure to the vapor. The liquid can cause blisters.
   Eyes Headaches have been reported following exposure to pentaborane or decaborane. Borohydrides have also caused irreversible eye damage.

First aid
   Ingestion Do not induce emesis. Activated charcoal: administer charcoal as a slurry (240 ml water/30 g charcoal). Usual dose: 25 to 100 g in adults/adolescents.
   Inhalation Move patient to fresh air. Monitor for respiratory distress. If cough or difficulty breathing develops, evaluate for respiratory tract irritation, bronchitis, or pneumonitis. Administer oxygen and assist ventilation as required. Treat bronchospasm with beta2 agonist and corticosteroid aerosols.
   Skin Remove and isolate contaminated clothing and shoes. In case of contact with substance, immediately flush with running water for at least 20 minutes.
   Eyes Irrigate exposed eyes with copious amounts of tepid water for at least 15 minutes. If irritation, pain, swelling, lacrimation, or photophobia persist, the patient should be seen in a health care facility.

UN number 1380
Response guide 135
Hazard class 4.2
Packing Group I  
Std. Transport # 4916138