Arsenic - Chemistry Encyclopedia
Artificial Sweeteners - Chemistry Encyclopedia
There are presently four artificial, or synthetic, sweeteners that have been approved by the U.S. Food and Drug Administration (FDA): saccharin, aspartame, acesulfame-K, and sucralose.
Ascorbic Acid - Chemistry Encyclopedia
Ascorbic acid or vitamin C is an antiscorbutic agent. Scurvy is a disease that potentially ranks as the second most important nutritional deficiency, after protein-calorie malnutrition.
Astatine - Chemistry Encyclopedia
Astrochemistry - Chemistry Encyclopedia
In the night sky, the expanses of space between the stars of the Milky Way appear to be empty. In fact this space is occupied by a very thin gas that is mostly hydrogen and that has mere traces (less than 0.1% by number of atoms) of other elements such as oxygen, carbon, and nitrogen.
Atmospheric Chemistry - Chemistry Encyclopedia
With each breath, the lungs inhale air filled with nitrogen and oxygen, the most abundant natural gases in the atmosphere. Also inhaled, however, are small quantities of gases and particles that are pollutants.
Atomic Nucleus - Chemistry Encyclopedia
The atomic nucleus is a tiny massive entity at the center of an atom. Occupying a volume whose radius is 1/100,000 the size of the atom, the nucleus contains most (99.9%) of the mass of the atom.
Atomic Structure - Chemistry Encyclopedia
The ancient Greek philosophers Leucippus and Democritus believed that atoms existed, but they had no idea as to their nature. Centuries later, in 1803, the English chemist John Dalton, guided by the experimental fact that chemical elements cannot be decomposed chemically, was led to formulate his atomic theory.
Atoms - Chemistry Encyclopedia
An atom is the smallest possible unit of an element. Since all forms of matter consist of a combination of one or more elements, atoms are the building blocks that constitute all the matter in the universe.
Barium - Chemistry Encyclopedia
Base Pairing - Chemistry Encyclopedia
James Watson and Francis Crick proposed the molecular structure of deoxyribonucleic acid (DNA) in 1952.
Bases - Chemistry Encyclopedia
Bases are considered the chemical opposite of acids because of their ability to neutralize acids. In 1887 the Swedish physicist and chemist Svante Arrhenius defined a base as the chemical substance that produces hydroxide ions (OH−) and cations.
Berkelium - Chemistry Encyclopedia
Beryllium - Chemistry Encyclopedia
Bioluminescence - Chemistry Encyclopedia
Bioluminescence is the emission of visible light by biological systems, which arises from enzyme-catalyzed chemical reactions. Bioluminescence can be distinguished from chemiluminescence in that it occurs in living organisms and requires an enzyme catalyst.
Bismuth - Chemistry Encyclopedia
Bleaches - Chemistry Encyclopedia
When chlorine gas is bubbled through a cylinder of tomato juice, the chlorine/tomato juice mixture turns almost completely white within five minutes. This spectacular change is a result of the chemical action of chlorine, acting as an oxidizing bleaching agent, on the pigments in tomato juice.
Avery, Oswald - Chemistry Encyclopedia
By the early 1940s, scientists knew that chromosomes existed and that they were composed of smaller units called genes. Chemical analysis had revealed that the eucaryotic chromosome consists of about 50 percent protein and 50 percent deoxyribonucleic acid (DNA).
Avogadro, Amedeo - Chemistry Encyclopedia
In 1811, just three years after John Dalton published his atomic theory, a brilliant theoretician named Amedeo Avogadro proposed his molecular theory. Avogadro's molecular theory related gas densities to molecular weights, explained reacting proportions by volume in terms of molecular ratios and compositions, and suggested methods for determining both molecular weights and compositions.
Baekeland, Leo - Chemistry Encyclopedia
Born in St. Martens-Latem, Belgium, Leo Hendrick Baekeland was the son of a cobbler (Karel Baekeland) and a housemaid (Rosalia Merchie).
Balmer, Johann Jakob - Chemistry Encyclopedia
The name of Johann Jakob Balmer is immortalized in the Balmer series of spectral lines emitted from the hydrogen atom. Atoms that are excited to higher energies return to lower energies by emitting electromagnetic radiation at specific frequencies.
Bardeen, John - Chemistry Encyclopedia
In 1972 John Bardeen did something that no other physicist, not even Albert Einstein, had ever done. He won his second Nobel Prize in physics.
Becquerel, Antoine-Henri - Chemistry Encyclopedia
Antoine-Henri Becquerel was born the son of the physicist Alexandre-Edmond Becquerel, and the grandson of the physicist Antoine-César Becquerel, and it is not surprising that he followed in their footsteps. It is also not surprising that his research interests centered around solar radiation and phosphorescence, as these are phenomena that his father had investigated.
Berg, Paul - Chemistry Encyclopedia
Paul Berg is considered to be one of the few pioneers in molecular biology, which is essentially the application of chemistry to biological systems. His work with recombinant DNA provided scientists with a very valuable laboratory technique.
Berthollet, Claude-Louis - Chemistry Encyclopedia
French chemist Claude-Louis Berthollet, developer of a chlorine-based bleach.
Berzelius, Jöns Jakob - Chemistry Encyclopedia
Before the early 1800s the symbols used to denote chemical elements and compounds were obscure. Alchemists wanted to keep their work secret and so devised symbols for the chemicals they used that would not reveal anything about them.
Black, Joseph - Chemistry Encyclopedia
Joseph Black was trained as a medical doctor. One of his early scientific undertakings was investigating means of treating "the stone" (kidney stones and gallstones).