Salt water for marine aquariums
Chemistry defines salt water-soluble ionic compounds in the form of crystals. Once the crystal comes into contact with water it splits and breaks down into its main constituents: anions (negatively charged ions) and cations (positively charged ions). When completely dissolved in water, they increase its ability to conduct current.
Once the dissolution of the salt has been obtained, obtain a SOLUTION which is defined as a dispersion of the solvent (water, in our case) of the solute (salt crystals). The solvent is the substance in greater quantity, while the solute is the substance, in our case it is more correct to say the substances, in smaller quantities.
The CONCENTRATION (salinity) of salt is the ratio between solute and solvent and can be chemically expressed in different ways, what is normally used is called mixed percentage, as it expresses the quantity in grams of salt dissolved in a liter. So saying 35 g / l means dissolving 35 grams of salt in a liter of water, not as we read in some documents I found on the internet that indicate dissolving 35 g in 0.965 liters of water, which would be equivalent to dissolving 36 , 27g / l.
If we consider the different seas and oceans of the world it can be seen that there are differences in concentration between the different areas, for example the Mediterranean sea has a concentration of 38 g / l, the red sea about 40g / l, the ocean Atlantic 37.5 g / l, while if we consider an average value that always facilitates operations we find our beautiful 35 g / l.
The international scale for the measurement of salinity was established at the end of 1978 in order to have a world reference of marine salinity for scientific studies; the scale is called PSU (acronym for Practical Salinity Units) where the ratio is estimated through the conductivity of a seawater sample with that of the standard solution of potassium chloride at 32.4356 g in one kg of water at a temperature of 15 ° C. There is no unit of measurement and 35 psu correspond exactly to 35 grams in 965 grams of water, for a total of 1 kg. This measurement method is the one used by manufacturers of controller and automation systems for aquariums.
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Salinity sea Surface |
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Salinity sea Surface from satellite |
TEMPERATURE is another very important factor for our marine reef aquariums. Considering the preparation of synthetic sea water we cannot but talk about it. All the compounds of the synthetic salt for aquariums are chemical raw materials (raw matirials), i.e. they are the basic elements (sodium, chlorine, calcium, magnesium, etc.) mixed together in order to recreate the composition of natural sea water (Natural Sea Water - N.S.W.) which contains about 78 different elements. Each raw material has an optimal dissolution temperature and usually varies with increasing temperature (direct solubility).
DENSITY is another parameter on which a lot is always written and is one of the most controversial. This parameter measures the tenacity of the bonds between molecules, and varies as a function of the salt concentration and temperature. The density that normal aquarium instruments measure is the RELATIVE DENSITY (specific gravity) which refers the density of salt water to a sample of pure water at 4 ° C and to an atmosphere. the value we find on the scale thus indicates how many times our water sample is heavier than pure water. The value has no unit of measure or you can put the abbreviation of the measure SG. I often find arguments based on nothing that argue about. (period) or on the, (comma): will you read 1.026 or 1.026? The question, as mentioned, does not exist since the point in the Anglo-Saxon context is equivalent to our comma, while we use it to express the thousands; and then logically our sample will not be able to weigh 1026 times pure water. The other possibility is that we express ourselves in kg / m3 instead of in g / cm3 and therefore we write the point of thousands which could also be omitted. What I always care a lot about is that the other two fundamental values Temperature and Pressure are placed together with the SG value. This is because, above all, as the temperature varies, the reported salinity value varies considerably.
You can get used to this simple UNESCO tools.
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