| MadSci Network: Chemistry |
Hi Todd: You asked if an acid or base that is powerful enough to be a health hazard is spilled on a surface, how long would it stay a threat? Dose it evaporate or eat on the surface until it runs out of ability. Things like drano/Liquid Plumber. Before I answer your question a few basics about acids and bases: ACID: A solution that has an excess of H+ ions. It comes from the Latin word "acidus" which means "sharp". BASE: A solution that has an excess of OH- ions. Another word for base is ALKALI. PH: is a handy way to express how acidic or alkaline a water solution is pH is measured on a scale of from 1 –14 with 7 being neutral. the closer you get to 1 the more acidic the material the closer you get to 14 the more basic. STRONG ACID: An acid which has a very low pH (0-4). STRONG BASE: A base which has a very high pH (10-14). WEAK ACID: An acid that only partially ionizes in an aqueous solution. That means not every molecule breaks apart. They usually have a pH close to 7 (3-6). WEAK BASE: A base that only partially ionizes in an aqueous solution. That means not every molecule breaks apart. They usually have a pH close to 7 (8-10). NEUTRAL: A solution which has a pH of 7. It is neither acidic nor basic. Acids: neutralize bases in a neutralization reaction. An acid and a base combine to form salts Bases: neutralize acids in a neutralization reaction. The word reaction is: Acid plus base makes water plus a salt. Bases denature protein. This accounts for the "slippery" feeling on hands when exposed to base. Strong bases that dissolve in water well, such as sodium or potassium lye are very dangerous because a great amount of the structural material of human beings is made of protein. Serious damage to flesh can be avoided by careful used of strong bases. Acids and Bases are collectively are called corrosives, corrosives cause visible destruction irreversible alterations to living tissue by chemical action at the point of contact. To answer your question the spilled acid or base will remain hazardous until it is neutralized, or diluted, made less concentrated. Acids and base solutions don’t evaporate very quickly. As they evaporate they become more concentrated. So their hazard may increase. --- Admin note: A few acid and base solutions become less concentrated as they evaporate, because the chemical that makes the acid or base is itself a gas. Examples are hydrochloric acid and ammonia. --- Depending on the surface, the acid can -- react with, combine with the material and form a salt as with metal, -- acids or base can react with the proteins in paper, cloth or wood and denature them, -- or the acid or base can just absorbed into the material and remain there creating a hazard for anyone who comes in contact with the material. So in summary an acid or base will remain hazardous until it is neutralized and changed into a salt or is greatly diluted. A rule of thumb is diluting to about 10:1 even then it still may present an irritation hazard. --- Admin note: there are several acid and base solutions that are extremely poisonous and dangerous, quite separately and for other reasons than their acid/base properties. These cannot be safely deactivated by this level of dilution. Examples are hydrofluoric or hydrocyanic acids. You should not be handling these substances at all. --- I hope I’ve answered you question. Thanks for writing to the Mad Scientist Network.
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