AskDefine | Define causticity

User Contributed Dictionary

English

Noun

  1. The quality of being caustic

Extensive Definition

A corrosive substance is one that will destroy or irreversibly damage another substance with which it comes in contact. The main hazards to people include damage to eyes, skin and tissue under the skin, but inhalation or ingestion of a corrosive substance can damage the respiratory and gastrointestinal tracts.
A low concentration of a corrosive substance is usually an irritant. Corrosion of non-living surfaces such as metals is a distinct process. For example, a water/air electrochemical cell corrodes iron to rust. In the Globally Harmonized System, both rapid corrosion of metals and chemical corrosion of skin qualify for the "corrosive" symbol.
Common corrosives are strong acids and strong bases, or concentrated solutions of certain weak acids and weak bases. Their action on living tissue is based on acid-base catalysis of ester and amide hydrolysis. Both corrosive acids and corrosive bases are able to defat skin by catalyzing the hydrolysis of fats, which are chemically esters). Proteins are chemically amides, which can also be hydrolyzed by acid-base catalysis. Strong acids and bases denature proteins and also hydrate easily. Hydration removes water from the tissue and is significantly exothermic. For example, concentrated sulfuric acid causes thermal burns in addition to chemical burns. Strong oxidizing agents, such as concentrated hydrogen peroxide, can also be corrosive to tissues and other materials, even when the pH is close to neutral. Nitric acid is an example of a strong acid that is also a strong oxidizer, making it significantly more corrosive than one would expect from its pKa alone.
There are also more specific corrosives. Hydrofluoric acid, for example, is initially painless but easily permeates tissue to selectively attack bone, making it extremely hazardous to work with. It is technically a weak acid, but it produces fluoride ion (the real corrosive species) after the acid is painlessly absorbed. Although zinc chloride solutions are also regularly acidic (by the Brønsted definition), the zinc cation also specifically attacks hydroxyl groups as a Lewis acid. This explains the ability of zinc chloride solutions to react with cellulose and corrode through paper and silk.
The word 'corrosion' is derived from the latin verb corrode which means 'to gnaw' indicating how these substance seem to 'gnaw' their way through the flesh.
Sometimes the word 'caustic' is used as a synonym, but by convention it generally refers only to strong bases as opposed to acids, oxidizers, or other non-alkaline corrosives.

Corrosive substances

Common corrosive chemicals are classified into:

References

causticity in German: Ätzende Stoffe
causticity in Portuguese: Corrosivo
causticity in Russian: Каустик
Privacy Policy, About Us, Terms and Conditions, Contact Us
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2
Material from Wikipedia, Wiktionary, Dict
Valid HTML 4.01 Strict, Valid CSS Level 2.1