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A method for separating liquid mixtures by vaporization and condensation. As a separation technique, distillation exploits the fact that when a liquid is partially vaporized the compositions of the two phases are different. By separating the phases…

A colored substance that imparts more or less permanent color to other materials. Dyes are generally water-soluble, although some are soluble only during application, after which they become insoluble. Colored water-insoluble substances are called…

The science dealing with the chemical changes accompanying the passage of an electric current, or the reverse process in which a chemical reaction is used as the source of energy to produce an electric current, as in a battery or fuel cell. Electric…

The migration of electrically charged particles in solution or suspension in the presence of an applied electric field. Each particle moves toward the electrode of opposite electrical polarity. For a given set of solution conditions, the velocity…

Volatile, fragrant oils obtained from plants. Essential oils are distinguished from those known as fixed oils, which are mainly triglycerides of fatty acids. Essential oils have been obtained from thousands of plants (Fig. 1) and are designated and…

Probably the best known of the alcohols, formula CH3CH2OH, it is also called alcohol, ethanol, grain alcohol, industrial alcohol, ethyl hydroxide, and methylcarbinol. Pure ethyl alcohol is a clear, colorless, and volatile liquid that is flammable…

An alkene, formula CH2=CH2. Ethylene (see illustration) is a colorless gas with a boiling point of −103.8°C and a melting point of −169°C. Ethylene is the most-produced organic chemical in the world and is used to make hundreds of products as well…

Fentanyl is a synthetic opioid analgesic (pain reliever) that resembles morphine in its action. However, its drug potency is approximately 50 to 100 times more powerful than that of morphine, leading to high rates of both addiction and overdose…

The study of the adverse effects of drugs and chemicals on various biological systems in a medical-legal context. The forensic toxicologist may work with a medical examiner or coroner in order to determine the role that a particular chemical…

An analytical technique for separating volatile components based on their boiling points and the rate at which they travel through a column containing an adsorbent phase. Most compounds with boiling points below about 250°C can be readily analyzed…

The universal constant R that appears in the ideal gas law. This law is given by Eq. (1), 1 where P is the pressure, V the volume, n the amount of substance, and T the thermodynamic (absolute) temperature. The gas constant is universal in that it…

A translucent, colorless, protein derived from the skin, white connective tissue, and bone of animals. Gelatin may be derived from chicken and fish; however, most gelatin comes from cattle and pigs. The principal uses of gelatin are in foods and…

The branch of quantitative chemical analysis in which a desired constituent is converted (usually by precipitation) to a pure compound or element of definite, known composition, and then weighed. In a few cases, a compound or element is formed which…

The time required for one-half of a given material to undergo chemical reactions. As a term, half-life is often used in nuclear physics to quantify the average time interval required for one-half of any quantity of identical radioactive atoms to…