General Description
SILICON TETRACHLORIDE(10026-04-7) is a colorless, fuming liquid with a pungent odor. SILICON TETRACHLORIDE(10026-04-7) is decomposed by water to hydrochloric acid with evolution of heat. SILICON TETRACHLORIDE(10026-04-7) is corrosive to metals and tissue in the presence of moisture. SILICON TETRACHLORIDE(10026-04-7) is used in smoke screens, to make various silicon containing chemicals, and in chemical analysis.
Reactivity Profile
Chlorosilanes, such as SILICON TETRACHLORIDE, are compounds in which silicon is bonded to from one to four chlorine atoms with other bonds to hydrogen and/or alkyl groups. Chlorosilanes react with water, moist air, or steam to produce heat and toxic, corrosive fumes of hydrogen chloride. They may also produce flammable gaseous H2. They can serve as chlorination agents. Chlorosilanes react vigorously with both organic and inorganic acids and with bases to generate toxic or flammable gases. This material is incompatible with alkali metals and dimethyl sulfoxide.
Hazard
Toxic by ingestion and inhalation, strong
irritant to tissue.
Health Hazard
Inhalation causes severe irritation of upper respiratory tract resulting in coughing, choking, and a feeling of suffocation; continued inhalation may produce ulceration of the nose, throat, and larynx; if inhaled deeply, edema of the lungs may occur. Contact of liquid with eyes causes severe irritation and painful burns; may cause permanent visual impairment. Liquid may cause severe burns of skin. Repeated skin contact with dilute solutions or exposure to concentrated vapors may cause dermatitis. Ingestion causes severe internal injury with pain in the throat and stomach, intense thirst, difficulty in swallowing, nausea, vomiting, and diarrhea; in severe cases, collapse and unconsciousness may result.
Fire Hazard
Behavior in Fire: Contact with water in foam applied to adjacent fires will produce irritating fumes of hydrogen chloride.
Description
Chlorosilanes (general formula RnHmSiCl4-n-m, where R is an
alkyl, aryl, or olefin group) are compounds in which silicon is
bound to between one and four chlorine atoms, bonds with
hydrogen and/or organic groups making its total number of
bonds up to four. Chlorosilanes react with water, moist air, and
steam, producing heat and toxic, corrosive hydrogen chloride
fumes. Contact between gaseous hydrogen chloride and metals
may release gaseous hydrogen, which is inflammable and
explosive. Chlorosilanes react vigorously with oxidizing agents,
alcohols, strong acids, strong bases, ketones, and aldehydes.
Chemical Properties
Clear colorless liquid
Production Methods
Manufactured directly by the reaction of chlorine on silicon
metal or ferrosilicon at 500C or silicon carbide.
Flammability and Explosibility
Notclassified
reaction suitability
core: silicon
Environmental Fate
Studies of rats subjected to acute inhalation of 10 structurally
similar chlorosilanes, including tetrachlorosilane, suggest that
the acute toxicity of chlorosilanes is largely due to the hydrogen
chloride hydrolysis product. The observed effects were similar
to those of HCl inhalation both qualitatively (clinical signs)
and quantitatively (molar equivalents of hydrogen chloride at
the atmospheric LC50).
Purification Methods
Distil it under vacuum and store it in sealed ampoules under N2. It fumes in moist air and is very sensitive to moisture. It is soluble in organic solvents. It is a strong irritant. [Schenk in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I pp 682-683 1963.]
Toxicity evaluation
Silicon tetrachloride is a colorless, noninflammable, volatile
liquid with a pungent, suffocating odor. It fumes in air and is
corrosive to metals and tissues in the presence of moisture. In
experiments at Argonne National Laboratory in which it was
mixed with water and stirred under room conditions, about
35% of the theoretical yield of HCl evolved as a gas in the first
minute. It also reacts very rapidly with alcohols, primary and
secondary amines, ammonia, and other compounds containing
active hydrogen atoms. Thermal decomposition or burning
may produce dense white clouds of silicon oxide particles and
hydrogen chloride.
Silicon tetrachloride is a by-product in the production of
polysilicon, the key component of sunlight-capturing wafers in
solar energy panels, and for each ton of polysilicon produced,
at least four tons of silicon tetrachloride liquid waste are
generated. Pollution by silicon tetrachloride has been reported
in China, associated with the increased demand for photovoltaic
cells that has been stimulated by subsidy programs.
Toxics Screening Level
The initial threshold screening level (ITSL) for silicon tetrachloride (CAS #10026-04-7) is 20 μg/m3 based on an annual averaging time. A second acute ITSL for silicon tetrachloride of 2,000 μg/m3 based on a 1-hour averaging time.
