10 Record(s)


In the physical sciences, a particle is a small localized object to which can be ascribed several physical or chemical properties such as volume or mass. The word particle is generic; no specific size is implied by the term. A particle should contain more than two atoms because the very well characterized mercury (I) species Hg22+ is always referred to as an ion by chemists and thus establishes a precedent. See also Nanoparticle.

Particle size

An idealized concept that assumes all particles in a suspension have the same geometric shape, and usually assumed to be spherical; the size of any given particles as determined by its diameter. Multiple methods exist to measure particle size, especially in the nanoscale, and these include Electron Microscopy, Dynamic Light Scattering, among others.

Parts per Million (PPM)

A unit of concentration, usually abbreviated; a way to quantify very low concentrations of substances. For example, 1 ppm is equivalent to 1 milligram per liter (abbreviated as mg/L), or 0.0001% concentration. Parts per Billion (PPB) and Parts per Trillion (PPT) are also commonly used to indicate and even lower concentrations. See our helpful chart on size, weight and Concentration at the nanoscale.


A pesticide is any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest. Though often misunderstood to refer only to insecticides, the term pesticide also applies to herbicides, fungicides, and various other substances used to control pests. Under United States law, a pesticide is also any substance or mixture of substances intended for use as a plant regulator, defoliant, or desiccant. Pesticides are now ubiquitous in most parts of the world, and water supplies.


In chemistry, a measure of the acidity or basicity of an aqueous solution, or of the molar Concentration of hydrogen ions in solution. Solutions less than pH 7 are called acidic, and those greater than pH 7 are basic or alkaline. Pure water has a pH very close to 7. Acidic and basic are two extremes that describe chemicals, just like hot and cold describe extreme temperatures. Mixing acids and bases can cancel out their extreme effects; much like mixing hot and cold water. A substance that is neither acidic nor basic is neutral. The pH scale ranges from 0 to 14. Each whole pH value is ten times stronger than the preceding value. For example, a pH of 4 is ten times more acidic than a pH of 5 and 100 times (10 times 10) more acidic than a pH of 6.


A publication which contains directions for identifying Compound medicines, usually published by a government agency, or by a medical or pharmaceutical society.

Pharmaceutical Grade Purified Water

Ultra-pure water which has been filtered to USP 23 or USP 24 level of purity. Because the absence of microbiological content is of importance, the water must be monitored and tested regularly to ensure it remains within industry limits.


One trillionth of a meter (1 pm=10-12 m), or 0.001nm. See our helpful chart on size, weight and Concentration at the nanoscale.


To fall out of suspension; the instability of a suspension.


A substance, typically produced by a bacterium, that produces fever when introduced or released into the blood