Gelignite

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Gelignite, more commonly referred to as blasting gelatin or simply blasting jelly, is an explosive material used in mining, as a safer alternative to dynamite.

Composition

Gelignite consists of 20-50% collodion-cotton (a syrup-like material consisting of nitrocellulose dissolved in ether or alcohol) mixed with nitroglycerin or EGDN, mixture often nicknamed "gelatine", 30-40% saltpetre (sodium nitrate or potassium nitrate), though some formulations use ammonium nitrate and the rest being wood pulp. The solid part of gelignite is sometimes called "dope". The exact composition depends on the type of gelignite necessary or by the manufacturer.

Other sources indicate 54%-63% nitroglycerine, 3%-5% collodion cotton, 26%-34% KNO3, 6%-9% wood meal and 0.5% chalk; another composition of the same name is 70% NH4NO3, 29.3% nitroglycerine, and 0.7% collodion cotton.

On average, gelignite consists of 65% gelatine and 35% solid material.[1]

Properties

Chemical

Gelignite burns slowly whne ignited, though a basting cap is required to detonate it.

Physical

Gelignite is a white-ish paste-like material, with a specific odor, though this is not universal. It does not dissolve in water, but may partially dissolve in organic solvents.

Explosive

Gelignite has an average detonation velocity of 6,500 m/s. Detonation of gelignite yields an average between 800 and 860 cubic meters of gas per kg or gelignite.[2]

It is more stable than dynamite, but can still suffer from "sweating". Its composition makes it easily moldable and safe to handle without protection, as long as it does not enter in contact to anything capable of detonating it.

Availability

Can be acquired by entities that posses explosive material license. In the United Kingdom, an explosives certificate, issued by the local Chief Officer of Police, is required for the possession and use of gelignite.

It is available under the name Frangex.

Preparation

Gelignite can be prepared by carefully dissolving nitrocellulose in a solvent, then carefully adding the nitrate ester, then the resulting slurry is mixed with the nitrate salt and the wood dust, until the desired consistency.

More information on its preparation can be found on this SM thread page.

Projects

  • Mining and blasting rocks

Handling

Safety

Gelignite is a powerful explosive and should be handled with care.

As it contains nitrate esters, skin contact will cause severe headaches.

Storage

Should be kept in a cool place, at constant temperature.

Disposal

Should be diluted with a proper solvent and carefully incinerated.

Alternatively, one can add it in lots of water in small bits and pour a diluted solution of NaOH to hydrolyze it.

See also

References

  1. Lectures on Explosives, Third Edition, 1902, by Willoughby Walke, p. 321
  2. Introduction to Tunnel Construction Applied Geotechnics Vol. 3, 2010, David Chapman, Nicole Metje, Alfred Stärk, p. 171

Relevant Sciencemadness threads