As an introduction to this article an obligatory question: What is natural seawater? If we leave aside the solid particles, gases and colloidal matter present in marine water, and we concentrate only on the dissolved organic matter, the result may be surprising for a few:
About Natural Seawater
As an introduction to this article an obligatory question:What
is natural seawater?
If we leave aside the solid particles, gases and colloidal matter present
in marine water, and we concentrate only on the dissolved organic matter,
the result may be surprising for a few:
So we can come to a little bit sad conclusion: 0,3% of mass makes
the difference between seawater and salt water for cooking of spaghetti...
Scientific research, commercial tests and everyday practice of marine
aquarists clearly reconfirms the validity of the following two laws (there
is more than one expression for both):
Shelford’s law of tolerance
Every organism is capable to survive within certain
limits of their living environment factors.
Liebig’s law of the minimum
If all conditions mentioned in Shelford’s law of tolerance
in the living environment of an organism are met and one is not, then this
one condition acts as the limiting factor.
Moreover, in case of marine water one has to acknowledge a very crucial
fact, regarding the concentration relationship between different marine
water constituents, e.g.:
H - Hydrogen - 1,07 . 102 mol/l
Ir - Iridium - 1,00 . 10-14 mol/l
The 16 digit places difference is essentially huge and urges the marine
water aquarists to apply relative thinking – one more example:
If we add 1 kg of common salt (NaCl) to a 1.000 litre tank, with a rather
high degree of certainty we can say that absolutely nothing will happen
– an NaCl mass concentration increase of c. 3% is absolutely within the
living environment factors limits for marine organisms according to Shelford’s
However this applies only in the case that NaCl is of a high purity and
does not contain for instance 0,001% of Cadmium. Although an impurity of
0,001% seems neglectable, it would lead to the increase of the Cadmium mass
concentration in the tank 120x with devastating results – one of the living
environment factors would get over the Shelford‘s law limits and become
a limiting one according to the Liebig’s law.
The facts mentioned above leads to the following conclusions:
When applying any substances into a tank, occurring there in relatively
high concentrations (base, major and minor elements) extreme attention
has to be paid to their purity.
When applying any substances into a tank, occurring there in relatively
low concentrations (trace elements and dissolved organic matter), extreme
attention has to be paid to their types and concentration ratios.
Anomalous properties of water
Water on its own is a interesting liquid, with many unexpected properties,
which defies chemical and physical theoretical expectations. Oxygen is
the first member of its elemental group in the periodic table, with the
lowest atomic number.
O – S – Se – Te
– Po (oxygen, sulphur, selenium, tellurium, polonium)
If we measure the boiling point of hybrids of these elements (compounded
with hydrogen), the temperature drops with the decreasing atomic weight
of the element and with water it should be the lowest. It is not, on the
contrary it is extremely high, the highest from the measured group. There
are a whole range of these type of so called anomalies in the properties
HIGH TEMPERATURE CAPACITY
Prohibits extreme temperature fluctuations/variances, produces with
the motion of water an above average heat conduction and in living organisms
enables the holding of a single temperature in the whole body.
HIGH SPECIFIC LATENT HEAT OF FUSION AND VAPORIZATION
It is the highest of all known solids and liquids except liquid
ammonia. It is necessary to add extremely high heat during the transition
of water from the solid state to liquid state and from the liquid state
to gaseous state. It is a key property for the transport of heat and
water in the atmosphere.
Both fresh and salt water reach their maximum
density above freezing point. This property is very important, for
example in the vertical circulation of water. With the dropping temperature
of water its density increases, but just before reaching freezing point
it starts to reduce again– which is why ice floats on water.
It is the highest amongst known liquids. This
property is key one for cellular processes.
HIGH DIELECTRIC CONSTANT
It enables dissociation of salts into electrolytes
(dissolving abilities). Water generally dissolves more materials and
in greater quantities than any other liquid. This property is key in
a whole range of physical and biological processes.
Relatively high. Water absorbs radiation energy
in the IR and UV range of the spectrum. In the visible spectrum absorbance
is however relatively low and is different for various wave lengths
– hence it is transparent. This property is also important for a range
of both physical and biological processes.
It is the highest amongst known liquids. Heating
water in one area does not cause a continuous increase of temperature,
the thermal energy is quickly transported to the rest of the remaining
contents. This is an important property for cellular processes.
There are many more of these exceptional properties of water, for
the above list were chosen only those whose effects can be simply explained.
From those it is clear that if even one of these didn’t exist then life
on earth also wouldn’t.
Natural Seawater Composition
Except the H20, seawater also contains:
SOLID MATERIALS (materials
not pass through a 0.45 µm filter)
organic (remains of living organisms)
inorganic (mineral particles)
inert ( nitrogen, argon and xenon)
active (oxygen and carbon dioxide)
COLLOIDS (materials that
through 0.45 µm filter, but isn’t soluble)
( Key for reefkeeping)
inorganic (base, major, minor and trace elements)
Dissociation, Equilibrium Etc.
If you assume that scientists know the exact make up of salt water
then you would be wrong. The reason - as touched upon in the previous chapter
- the high dielectric constant of water, enables the dissociation of salts
into electrolytes and the fact that water its self as H2O has a very complicated
molecular structure, which has been the thesis of many sets of dissertation
However for the purposes of this article it is enough the stated fact
that water thanks to its large capabilities for dissolving, breaks down
molecules of various salts into cations and anions (e.g. NaCl into Na+
and Cl- ) and these in part react with the water itself and in part with
the cations and anions of other dissolved salts. This process of ion interaction
is dynamic. The concrete make up of salt water is constantly changing in
dependence with a whole range of conditions, mainly temperature, salinity
and pH level.
It can be demonstrated with the following very simple example. To water
we add kitchen salt (NaCl) and magnesium sulphate (MgSO4), where we know
that neither of afore mentioned chemicals were present before. After dissolving
the salts and following precise analysis, we could expect that the results
confirm the make up of the solution as:
H2O - NaCl - MgSO4
This most certainly won’t happen – analysis also confirms the presence
The results are markedly more complicated than we would most likely expect,
and this example only involved water with two salts dissolved in it – salts
and ions however enter salt water in hundreds chemicals from various sources
and it is basically possible to identify every element of the periodic table
From the facts given above also comes a very unpleasant result for the
producers of sea salts – sea salt can’t be produced with chemicals in proportion
to that from the results of the analysis of salt water. Among other reasons,
because wide range of molecules is very unstable or is impossible to prepare
To conclude we will again give a short example:
Copper (Cu) is found in salt water in the following
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