Dynamite is an important industrial explosive. It has been used to blast out damsites, canal beds, mines, quarries, and the foundations for large buildings. Dynamite also has been used for demolition in warfare.
The principal explosive in dynamite is an oily liquid called nitroglycerin. It is mixed with other materials—some explosive and some nonexplosive—and packed in cylinders made of waxed paper or plastics. These cylinders, called cartridges, range from 7/8 to 8 inches (22 to 200 millimeters) in diameter and from 4 to 30 inches (10 to 76 centimeters) in length.
To use dynamite, workers insert an explosive device called a detonating cap or blasting cap into one end of the cartridge. They place the cartridge in a hole bored into the material to be blasted. Earth is packed around and behind the cartridge. After moving to safety, the workers set off the detonating cap—and the explosion—by means of a fuse or an electric current.
Kinds of dynamite.
There are four chief varieties of dynamite. They are (1) straight dynamite, (2) ammonia dynamite, (3) straight gelatin, and (4) ammonia gelatin.
Straight dynamite contains nitroglycerin and an absorbent, chemically reactive mixture, such as wood pulp and sodium nitrate. It is the oldest dynamite type and has been replaced by ammonia dynamite for most uses.
Ammonia dynamite is stronger, safer, and cheaper than straight dynamite. It contains ammonium nitrate and produces cooler gases and fewer toxic fumes than other dynamites do. It is called a permissible explosive, which means that it can be used safely in mines where extreme heat could ignite dust or gas in the air.
Straight gelatin is made from a stiff gel called blasting gelatin. Blasting gelatin consists of nitroglycerin mixed with a small amount of an explosive called guncotton (see Guncotton). Sodium nitrate and other ingredients are added to make straight gelatin. Straight gelatin has been replaced by ammonia gelatin for most uses.
Ammonia gelatin is made by adding ammonium nitrate and other ingredients to blasting gelatin. Ammonia gelatin is waterproof. It is used for underwater and hard-rock blasting.
History.
Dynamite was patented in 1867 by Alfred Nobel, a Swedish chemist and the founder of the Nobel Prizes. Nobel discovered that kieselguhr, a type of chalky earth, absorbed a great deal of nitroglycerin. He found that kieselguhr soaked with nitroglycerin served as an explosive that was less dangerous to handle than pure nitroglycerin. It also was much more powerful than the gunpowder explosives then used for blasting. From his discovery, Nobel developed straight dynamite and blasting gelatin.
In the early 1900’s, ammonia dynamite and ammonia gelatin were developed. In the 1950’s, many blasting operators began to use a mixture of ammonium nitrate and fuel oil, called ANFO, instead of dynamite. ANFO and a chemical mixture called emulsion explosive are the most widely used industrial explosives today. They are cheaper to use than dynamite. They are also extremely insensitive (difficult to set off), requiring dynamite or other explosives to detonate them.
See also Explosive; Fuse; Nitroglycerin; Nobel, Alfred B.; TNT.
