General Catalogue Chemistry - BECO Internacional LTDA.

Osmosis/diffusion
Osmosis is a special instance of diffusion in
which the molecules of a solvent (water in the
simplest case) diffuse through a (semipermeable)
membrane. If such a membrane separates
two solutions of differing concentrations, solvent
molecules will migrate through the membrane
toward the higher-concentration solution
until the concentrations have reached equilibrium.
This process increases the hydrostatic pressure
in the solution which had previously been
more concentrated. The pressure which prevails
at the conclusion of this process is referred to as
the osmotic pressure. Osmotic pressures are of
great significance, above all in biological systems
(across the cell walls).
662 403
Osmosis apparatus/lens model
The osmosis apparatus is used for quick and
easy demonstration of osmotic pressure. It is
supplied ready for use; cleaning is simple.
Two liquids of differing concentration are separated
by a large semipermeable membrane;
the size of the membrane causes an especially
rapid rise in hydrostatic pressure which is
indicated by the capillary tube with the scale
behind it.
Scope of delivery
2 Mounting frames
2 Osmosis vessels (transparent)
4 Mounting rods with 8 knurled nuts
3 Films
5 Semipermeable membranes
2 Capillary tubes, 300 x 8mm
2 Rubber stoppers, SB 19 with hole
2 Rubber stoppers, SB 19 for electrodes
special topics
The “chemical crystalline garden” shown on this
page is an impressive example of such osmotic
processes. The surface of metallic salts reacts
with sodium silicate (water glass), forming silicates
and at the same time creating a semipermeable
skin at the surface which allows water to
penetrate. A hydrostatic pressure develops inside
this skin, causing the skin to rupture. Concentrated
salt solution is discharged, again reacting
with the sodium silicate. This process repeats itself
continuously. In this way a collection of
rapidly growing chemical “plants” is created.
Accessories and spares
667 501
Scale for osmosis apparatus
With mm divisions and 5 cm marking.
Length: 300 mm
667 503
Pig bladder
To demonstrate the permeability of a
natural membrane.
667 512
Membranes
Semipermeable, set of five.
667 513
Cation-permeable membrane
To demonstrate the principle of an ion pump.
LEYBOLD DIDACTIC · GENERAL CATALOGUE CHEMISTRY
Osmosis
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