Nitric Acid: Nitric acid (HNO3). A colorless liquid that is used in the manufacture of inorganic and organic nitrates and nitro compounds for fertilizers, dye intermediates, explosives, and many different organic chemicals. Continued exposure to vapor may cause chronic bronchitis; chemical pneumonitis may occur. (From Merck Index, 11th ed)Spectrophotometry, Atomic: Spectrophotometric techniques by which the absorption or emmision spectra of radiation from atoms are produced and analyzed.Neodymium: Neodymium. An element of the rare earth family of metals. It has the atomic symbol Nd, atomic number 60, and atomic weight 144.24, and is used in industrial applications.Decalcification Technique: Removal of minerals from bones during bone examination.Hydrofluoric Acid: Hydrofluoric acid. A solution of hydrogen fluoride in water. It is a colorless fuming liquid which can cause painful burns.Sulfuric Acids: Inorganic and organic derivatives of sulfuric acid (H2SO4). The salts and esters of sulfuric acid are known as SULFATES and SULFURIC ACID ESTERS respectively.Trace Elements: A group of chemical elements that are needed in minute quantities for the proper growth, development, and physiology of an organism. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Hydrochloric Acid: A strong corrosive acid that is commonly used as a laboratory reagent. It is formed by dissolving hydrogen chloride in water. GASTRIC ACID is the hydrochloric acid component of GASTRIC JUICE.Nitrates: Inorganic or organic salts and esters of nitric acid. These compounds contain the NO3- radical.Microwaves: That portion of the electromagnetic spectrum from the UHF (ultrahigh frequency) radio waves and extending into the INFRARED RAYS frequencies.Calibration: Determination, by measurement or comparison with a standard, of the correct value of each scale reading on a meter or other measuring instrument; or determination of the settings of a control device that correspond to particular values of voltage, current, frequency or other output.Environmental Monitoring: The monitoring of the level of toxins, chemical pollutants, microbial contaminants, or other harmful substances in the environment (soil, air, and water), workplace, or in the bodies of people and animals present in that environment.