Sulfuric Acid

Sulfuric Acid, corrosive, oily, colorless liquid, with a specific gravity of 1.85. It melts at 10.36° C (50.6° F), boils at 340° C (644° F), and is soluble in all proportions in water. When sulfuric acid is mixed with water, considerable heat is released. Unless the mixture is well stirred, the added water may be heated beyond its boiling point and the sudden formation of steam may blow the acid out of its container (see Acids and Bases). The concentrated acid destroys skin and flesh, and can cause blindness if it gets into the eyes. The best treatment is to flush away the acid with large amounts of water. Despite the dangers created by careless handling, sulfuric acid has been commercially important for many years. The early alchemists prepared it in large quantities by heating naturally occurring sulfates to a high temperature and dissolving in water the sulfur trioxide thus formed. About the 15th century a method was developed for obtaining the acid by distilling hydrated ferrous sulfate, or iron vitriol, with sand. In 1740 the acid was produced successfully on a commercial scale by burning sulfur and potassium nitrate in a ladle suspended in a large glass globe partially filled with water.

Sulfuric acid is a strong acid, that is, in aqueous solution it is largely changed to hydrogen ions (H+) and sulfate ions. Each molecule gives two H+ ions, thus sulfuric acid is dibasic. Dilute solutions of sulfuric acid show all the behavior characteristics of acids. They taste sour, conduct electricity, neutralize alkalies, and corrode active metals with formation of hydrogen gas. From sulfuric acid one can prepare both normal salts containing the sulfate group and acid salts containing the hydrogen sulfate group.

Smog

Smog, mixture of solid and liquid fog and smoke particles formed when humidity is high and the air so calm that smoke and fumes accumulate near their source. Smog reduces natural visibility and often irritates the eyes and respiratory tract. In dense urban areas, the death rate usually goes up considerably during prolonged periods of smog, particularly when a process of heat inversion creates a smog-trapping ceiling over a city.

Smog prevention requires control of smoke from furnaces; reduction of fumes from metal-working and other industrial plants; and control of noxious emissions from automobiles, trucks, and incinerators. In the U.S. internal-combustion engines are regarded as the largest contributors to the smog problem, emitting large amounts of contaminants, including unburned hydrocarbons and oxides of nitrogen. The number of undesirable components in smog, however, is considerable, and the proportions highly variable. They include ozone, sulfur dioxide, hydrogen cyanide, and hydrocarbons and their products formed by partial oxidation. Fuel obtained from fractionation of coal and petroleum produces sulfur dioxide, which is oxidized by atmospheric oxygen, forming sulfur trioxide. Sulfur trioxide is in turn hydrated by the water vapor in the atmosphere to form sulfuric acid.

The so-called photochemical smog, which irritates sensitive membranes and damages plants, is formed when nitrogen oxides in the atmosphere undergo reactions with the hydrocarbons energized by ultraviolet and other radiations from the sun. See Air Pollution.