Reactive Group Datasheet
Metals, Elemental and Powder, Active
Materials in this group are combustible and can become dust explosion hazards, especially as finely divided powders. Powdered iron has exploded in the presence of air, moisture, and small amounts of organic impurities.
All of these materials are reducing agents and tend to react with oxidizing agents. Their reactivity is strongly influenced by their state of subdivision: in bulk they often resist chemical combination; in powdered form they may react very rapidly. Thus, bulk aluminum is used as a structural metal, but finely divided aluminum is pyrophoric. The effect of subdivision is due to the rapid reaction of these materials with oxygen to form relatively inert oxide layers. This layer of oxide can act as a passivating layer for the bulk metal, but the high surface area of the powder form along with the heat of reaction for oxide formation can ignite the metal.
Many of these materials react exothermically with compounds that have active hydrogen atoms (such as acids and water) to form flammable hydrogen gas and caustic products. The reactions are less vigorous than the similar reactions of alkali metals, but the released heat can still ignite the released hydrogen. Materials in this group may react with azo/diazo compounds to form explosive products. These metals and the products of their corrosion by air and water can catalyze polymerization reactions in several classes of organic compounds; these polymerizations sometimes proceed rapidly or even explosively. Some metals in this group form explosive products with halogenated hydrocarbons.
Caustic products formed from the corrosion of some of these metals by air or water can cause chemical burns. Inhalation of metal powders, dusts and fumes can cause serious symptoms. Even metals that are less toxic by inhalation (such as zinc) often contain toxic impurities (cadmium, antimony, arsenic, and lead). Iron dust causes conjunctivitis and lodges in the lungs to induce cancers.
Many alloys of these metals exist and have structural uses. The metals are used chemically as reducing agents. The metals and their compounds are used as catalysts in the synthesis of plastics, rubber, pharmaceuticals, and pesticides.
Aluminum, aluminum ferrosilicon, antimony, beryllium, calcium silicon, cerium, chromium, cobalt, gallium, hafnium, iron, magnesium alloy, nickel catalyst, selenium, silicon, strontium, titanium, zinc, zirconium.