Suspension (chemistry)

A suspension (Latin suspendere, hang up ',' in limbo leave ') is a heterogeneous mixture of a liquid and is finely divided solids in the fluid with suitable equipment ( stirrer, dissolver, liquid abrasive blasting, wet mill ) and usually use one or more dispersants are suspended and held in abeyance. A suspension of a coarsely dispersed and the dispersion tends to sedimentation and phase separation. The solids are " suspergiert " in the liquid phase.

Suspensions in water is referred to in materials science, or of natural occurrence as a slurry or (from the English ) slurry. They are divided into 'rough' suspensions ( particle size 0.1 mm to 1 mm, for example, chalk mud ) and "fine" suspensions ( particle size of 1 micron to 100 microns, such as milk of lime ). Still fine dispersed particles (less than 1 micron ) are dispersions of less than 1 nm molecular dispersions.

Suspensions or dispersions in polymer chemistry are feinstdispergierte polymer products which are obtained by suspension polymerization, for example, polyacrylates or vinyl acetates.

Sedimentation

Leaving a suspension are so decreases (as opposed to a solution ) is a solid with a greater density than the pure liquid at not too small particle size slowly to the ground, forming a sediment ( sedimentation). The supernatant liquid decanted can ( decant ) and thus the solids (sediment) from the liquid ( decantate ) are separated. The addition of so-called thixotropic agents or surfactants sedimentation may be slow, be accelerated by the addition of flocculants.

The stability of a suspension can be defined with a sedigraph, the settling velocity of different particles measured by the Stokes' law.

The smaller the particle, the lower its density and the higher the fluid viscosity, the slower the sedimentation proceeds. Also the shape and structure of the particles and other properties of particles and liquid affect the sedimentation.

Sedimentation can be accelerated by centrifugal.

A method to determine the material properties or the particle size and its distribution is the ultrasonic attenuation spectroscopy.

Examples

Examples of suspensions are:

  • Slurries of sand in sea water, suspended solids, or quicksand
  • Mortar or concrete (mineral suspensions)
  • Suspensions of silicon carbide and polyethylene glycol, which act simultaneously abrasive and cooling, are used in the photovoltaic industry and the semiconductor industry to cut pure silicon into wafers.
  • Body color, paint ( pigment suspensions, in distinction to dyes that go into solution )
  • Blood
  • The photographic light-sensitive layer on the film or photographic paper (which in the technical language (incorrectly) referred to as " emulsion " )
  • Pollen in honey aqueous solutions which are prepared for microscopic Palynology
  • Wheat beer
  • Orange juice
  • Sweetened milk cocoa is not just a suspension with particles of the mixture of cocoa ingredients, but also for example an aqueous sugar solution and an aqueous fat emulsion is therefore correctly described by the umbrella term " dispersion in a sugar solution ."
  • Drilling fluid

Substances which sediment in the suspensions mentioned, make with the liquid residue a suspension that liquid residue may also be a dispersion ( without sedimentation) again, an emulsion and a solution

For example, although cow's milk is a dispersion of milk fat and protein in water, are also suspensions, the " milky " look like " milk " means, for example,

  • Runoff water, a slurry of rock abrasion in glacial water,
  • Lime water, a slurry of slaked lime in water
  • Scouring milk, flour fine abrasive mixed in surfactant solutions or solvents.

Suspensions in medicine

For medical suspensions insoluble powder as drugs are suspergiert in carrier liquids. The immiscibility of the components may result in contrast to a complete solution to segregation by lowering the solid particles due to gravity. Suspensions are therefore seen macroscopically homogeneous only if they are easily and quickly aufschüttelbar.

Such suspensions shall apply

  • Into the body openings
  • On the eye
  • Externally
  • Intramuscularly
  • Inwardly
Phase (matter) Wafer (electronics) Butterfat Fluvio-glacial Hard-surface cleaner#Scouring agents Active ingredient Homogeneity (physics)
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