CAS 7553-56-2





Physical Properties

Blue-violet to black crystalline solid

bp 185 °C, mp 114 °C

Slightly soluble in water (0.03 g/100 mL at 20 °C)



Sharp, characteristic odor


Vapor Density

8.8 (air = 1.0)


Vapor Pressure

0.3 mmHg at 20 °C


Flash Point



Toxicity Data

LD50 oral (rat)

14,000 mg/kg


LCLO inhal (rat)

80 ppm (800 mg/m3; 1 h)



0.1 ppm (ceiling, 1 mg/m3)



0.1 ppm (ceiling, 1 mg/m3)

Major Hazards

Iodine vapor is highly toxic and is a severe irritant to the eyes and respiratory tract.


The acute toxicity of iodine by inhalation is high. Exposure may cause severe breathing difficulties, which may be delayed in onset; headache, tightness of the chest, and congestion of the lungs may also result. In an experimental investigation, four human subjects tolerated 0.57 ppm iodine vapor for 5 min without eye irritation, but all experienced eye irritation in 2 min at 1.63 ppm. Iodine in crystalline form or in concentrated solutions is a severe skin irritant; it is not easily removed from the skin, and the lesions resemble thermal burns. Iodine is more toxic by the oral route in humans than in experimental animals; ingestion of 2 to 3 g of the solid may be fatal in humans.

Iodine has not been found to be carcinogenic or to show reproductive or developmental toxicity in humans. Chronic absorption of iodine may cause insomnia, inflammation of the eyes and nose, bronchitis, tremor, rapid heartbeat, diarrhea, and weight loss.

Flammability and Explosibility

Iodine is noncombustible and in itself represents a negligible fire hazard when exposed to heat or flame. However, when heated, it will increase the burning rate of combustible materials.

Reactivity and Incompatibility

Iodine is stable under normal temperatures and pressures. Iodine may react violently with acetylene, ammonia, acetaldehyde, formaldehyde, acrylonitrile, powdered antimony, tetraamine copper(II) sulfate, and liquid chlorine. Iodine

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement