Lead azide

Description

Lead azide is a severe explosion risk and should be handled under water; it is also a primary detonating compound.

Chemical Properties

needles or white powder(s); prepared by reaction of dilute solutions of lead nitrate and sodium azide; used as a primary detonating compound for high explosives; α-Pb(N3)2: orthorhombic, a=0.663nm, b=0.546 nm, c=1.625nm; β-Pb(N3)3: monoclinic, a=0.509 nm, b=0.884nm, c=1.751 nm; γ-Pb(N3)2: a=0.622nm, b=1.051 nm, c=1.217 nm [MER06] [CIC73] [KIR78]

Physical properties

Colorless needles or white powder; density ~4.0 g/cm³; explodes on heating at 350°C; slightly soluble in water, 230 mg/L at 18°C and 900 mg/L at 70°C; very soluble in acetic acid; insoluble in ammonia solution.

Uses

As primer in explosives. In the form of dextrinated lead azide.

Production Methods

Lead azide crystallizes as colorless needles. It is a sensitive detonating agent, exploding at 350 °C. Lead azide is commonly prepared by the reaction between dilute solutions of lead nitrate and sodium azide. For safety, it is stirred vigorously to prevent formation of large crystals, which may detonate. Lead azide is usually precipitated with a protective material, such as gelatin, and then granulated. Lead azide is also used to prepare electrophotographic layers and for information storage on styrene–butadiene resins.

Preparation

Lead azide is prepared by the reaction of sodium azide with lead nitrate:
2NaN₃ + Pb(NO₃)₂ → Pb(N₃)₂ + 2NaNO₃
.

General Description

Needles or white powder. Explodes at 350°C. Insoluble in water. May explode from shock, heat, flame or friction when dry. The primary hazard is the blast effect of an instantaneous explosion and not flying projectiles and fragments.

Air & Water Reactions

Insoluble in water.

Reactivity Profile

Lead azide is unstable. May, when dry, decompose explosively if shocked, heated or subjected to friction. Forms violently explosive products with carbon disulfide. Can be sensitized to explosive decomposition by metal salts (copper or zinc) or by traces of strong acids [Sax, 9th ed., 1996, p. 298]. An explosion occurred by mixing Lead azide with 0.5% of calcium stearate, [MCA Case History No. 949].

Hazard

Lead azide explodes on heating at 350°C or on percussion. Its detonation velocity is 5.1 km/sec (Meyer, E. 1989. Chemistry of Hazardous Materials, 2^nd ed. Englewood Cliffs, N.J.: Prentice Hall). It undergoes violent explosive reaction with carbon disulfide and forms shock-sensitive copper and zinc azides when mixed with the solutions of copper and zinc salts (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, 2^nd ed. New York: John Wiley).

Health Hazard

Toxicity data for lead azide are not available.Its aqueous solution is toxic, exhibitingpoisoning effect of lead.

Fire Hazard

MAY EXPLODE AND THROW FRAGMENTS 1600 meters (1 MILE) OR MORE IF FIRE REACHES CARGO.

Carcinogenicity

Results in an early study were deemed inconclusive because dose levels were not considered high enough. Rats were fed diets containing 100 or 200 ppm (6 or 12 mg/kg/day) sodium azide for 18 months followed by 6 months of observation. An increase in pituitary adenomas in the low-dose females compared to concurrent controls was found, but in this study the incidence in the control rats was unusually low compared to historical controls. A similar result occurred with mammary tumors.
No carcinogenicity studies were found for hydrogen azide or lead azide but lead should be used as an analog for the latter chemical.

Waste Disposal

Lead azide is decomposed by treatment withnitrous acid or ceric ammonium nitrate (Wear1981).

Raw materials

Preparation Products