LABORATORY CHEMICAL SAFETY SUMMARY: LITHIUM ALUMINUM HYDRIDE

Substance

Lithium aluminum hydride

(LAH, lithium tetrahydroaluminate)

CAS 16853-85-3

 

Formula

LiAlH4

 

Physical Properties

White to gray crystalline solid

Decomposes above 125° C

Reacts vigorously with water

 

Odor

Odorless solid

 

Autoignition Temperature

Ignites in moist or heated air

 

Toxicity Data

TLV-TWA (ACGIH)

2 mg (Al)/m3

Major Hazards

Reacts violently with water, acids, and many oxygenated compounds; may ignite in moist air; corrosive to skin, eyes, and mucous membranes.

Toxicity

Lithium aluminum hydride is highly corrosive to the skin, eyes, and mucous membranes. Contact with moisture forms lithium hydroxide, which can cause severe burns. Powdered LAH forms dusts that can pose an inhalation hazard. Ingestion of this substance may cause aching muscles, nausea, vomiting, dizziness, and unconsciousness and may be fatal. Ingestion can result in gas embolism due to the formation of hydrogen.

No chronic effects of lithium aluminum hydride have been identified.

Flammability and Explosibility

Lithium aluminum hydride is a highly flammable solid and may ignite in moist or heated air. Exposure to water results in the release of hydrogen, which can be ignited by the heat from the exothermic reaction. Lithium aluminum hydride should not be used as a drying agent for solvents because fires can easily result (LAH decomposes at about 125° C, a temperature easily reached at a flask's surface in a heating mantle). The decomposition products of LAH can be quite explosive, and the products of its reaction with carbon dioxide have been reported to be explosive. Use dry chemical powder or sand to extinguish fires involving lithium aluminum hydride. Never use water or carbon dioxide extinguishers on an LAH fire.

Reactivity and Incompatibility

Lithium aluminum hydride reacts violently with water, acids, oxidizers, alcohols, and many oxygenated organic compounds, including, in particular, peroxides, hydroperoxides, and peracids. LAH reacts with many metal halides to produce metal hydride products, which are flammable and toxic.

Storage and Handling

Lithium aluminum hydride should be handled in the laboratory using the "basic prudent practices" described in Chapter 5.C, supplemented by the additional precautions for work



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