N rod bit: A Canadian standard noncoring bit having a set diameter of 2.940 inches (74.676 millimeters).
N-P-K: The code identifying the components in a fertilizer mixture: nitrogen (N), phosphorus pentoxide (P), and potassium oxide (K). Fertilizers are graded in the order N-P-K, with the numbers indicating the percentage of the total weight of each component. For
Nansen bottle: A bottlelike water-sampling device with valves at both ends that is lowered into the water by wire, at the desired depth it is activated by a messenger which strikes the reversing mechanism and inverts the bottle, closing the valves and trapping the water
natural-gasoline plant: Compression, distillation, and absorption process facility used to remove natural gasoline (mostly butanes and heavier components) from natural gas.
nautical chain: A unit of length equal to 15 feet or 4.572 meters.
naval architecture: The study of the physical characteristics and the design and construction of buoyant structures, such as ships, boats, barges, submarines, and floats, which operate in water, includes the construction and operation of the power plant and other mechanical
Navier's equation: A vector partial differential equation for the displacement vector of an elastic solid in equilibrium and subjected to a body force.
navigation dam: A structure designed to raise the level of a stream to increase the depth for navigation purposes.
Nelson diaphragm cell: Obsolete carbon-electrode type of electrolytic diaphragm cell once widely used to produce chlorine and caustic soda from brine.
Nernst approximation formula: An equation for the equilibrium constant of a gas reaction based on the Nernst heat theorem and certain simplifying assumptions.
Nernst heat theorem: The theorem expressing that the rate of change of free energy of a homogeneous system with temperature, and also the rate of change of enthalpy with temperature, approaches zero as the temperature approaches absolute zero.
Nernst-Lindemann calorimeter: A calorimeter for measuring specific heats at low temperatures, in which the heat reservoir consists of a metal of high thermal conductivity such as copper, to promote rapid temperature equalization, none of the material under study is more than a few mil
Nernst-Simon statement of the third law of thermodynamics: The statement that the change in entropy which occurs when a homogeneous system undergoes an isothermal reversible process approaches zero as the temperature approaches absolute zero.