M or Molar: A molar solution consists of one gram molecular weight of a compound dissolved in enough water to make one litre of solution. A gram molecular weight is the molecular weight of a compound in grams. For example, the molecular weight of sulphuric acid (H2SO4) is 98. A one M solution of sulphuric acid would consist of 98 grams of H2SO4 dissolved in enough distilled water to make one litre of solution.
Material Safety Data Sheet (MSDS): A Material Safety Data Sheet (MSDS) describes the properties and uses of a particular hazardous substance. There are details about the chemical and physical properties of the substance, health hazard information, and precautions for use and safe handling information. For employers, there is a legal obligation to obtain a MSDS on or before the first supply of the hazardous substance. The MSDS should be accessible to all employees and displayed as near as possible to the point of use. Employees should comply with all safety precautions.
Melting point: The melting point
is the temperature at which a solid becomes a liquid at standard atmospheric
pressure. The melting point and freezing point of a pure substance are
the same temperature. Pure substances melt at constant temperature. The
melting point graph for a pure substance is horizontal as the solid melts.
Impurities lower the melting point. The melting point graph for an impure
substance has an inclined line as the solid melts. Melting points and
melting behaviours can be used to identify a substance and determine
its purity.
Meniscus (MUH-NISS-cuss): The curved
top of a column of liquid (water, oil, mercury) in a small tube. When the
liquid wets the sides of the container (as with water), the curve forms
a valley - read the bottom of the curve. When the confining sides are not
wetted (as with mercury), the curve forms a hill or upward bulge - read
the top of the curve.
Microbes: Another term for micro-organism, which is an organism that is too small to be seen with the unaided eye (eg microscope).
Microbial: A description for an organism that is a micro-organism.
Microbiological Characteristics: The characteristics or attributes of micro-organisms.
Micro-organisms: Microscopic organisms ('microbes'), either plant or animal, generally not visible to the naked eye. Include bacteria, fungi, protozoas and viruses.
Milligrams per Litre, mg/L: Substance
per unit volume. For practical purposes one mg/L of a substance in fresh
water is equal to one part per million parts (ppm). Thus a litre of water
with a specific gravity of 1.0 weighs one million milligrams. If it contains
10 milligrams of calcium, the concentration is 10 milligrams per million
milligrams, or 10 milligrams per litre (10mg/L), or 10 parts of calcium
per million parts of water, or 10 parts per million (10ppm).
Mixing time: The time over which
mixing takes place ranging from seconds in flash mixing to minutes in
flocculation mixing.
Metal based coagulant: Metal based coagulants usually contain aluminium or iron. Metal based coagulants work by disassociating into metal ions, which are then attracted to the surface of the colloids and work to reduce the forces that keep them apart so that floc can form. Then by forming metal hydroxides which precipitate out of solution and form nuclei for colloids to settle on (ie form floc).
Molecular weight: The molecular
weight of a compound in grams is the sum of the atomic weights of the
elements in the compound. The molecular weight of sulphuric acid (H2SO4)
in grams is 98.
Molecule (MOLL-uh-kule): The smallest division of a compound that still retains or exhibits all the properties of the substance.
MSDS (pronounced as separate letters): MSDS stands for Material Safety Data Sheet. A MSDS describes the properties and uses of a particular hazardous substance. There are details about the chemical and physical properties of the substance, health hazard information, and precautions for use and safe handling information. For employers, there is a legal obligation to obtain a MSDS on or before the first supply of the hazardous substance. The MSDS should be accessible to all employees and displayed as near as possible to the point of use. Employees should comply with all safety precautions.