thawing salt (also salt for melting snow called) exists usually to 95 per cent of conventional common salt and in the winter to melting snow and ice on traffic routes is used. Thus the evacuation of snow concerns a measure.
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the commercial thawing salt consists to a large extent of cook or rock salt, thus sodium chloride (NaCl). Besides it contains natural sliding materials such as gypsum (calcium sulfate), sliding gel or clay/tone. Thawing salt is usually used only on public, städtlichen and federal highways.
the effect of the thawing salt is connected with its molecular melting point degradation . One makes too uses oneself that solutions have a smaller melting point than pure liquids. After covering the ice with thawing salt develops a solution of salt in water, which exhibits a lower melting point than the pure ice and remains liquid at lower temperatures.
In addition the ice is in an equilibrium, similarly as when evaporating water, between the states of aggregation celebration and liquid (it is it is extremely cold, which occurs quite rarely however in Germany). Thus always melts a certain quantity ice, which freezes then normally again. Here the ions of the salt loosened in the water film serve as interference factor and prevent a renewed “union” from the crystalline structure of the water (ice). Since however still the same quantity water of the ice melts, but any longer to freeze, does not dissolve the ice can slowly.
The thawing salt prevents thus above all the renewed freezing of the meltwater.
Conventional common salt is suitable well with few minus degrees as thawing salt. Off approx. -10 °C is other salts as for instance the environmentalmore harmful calcium chloride or magnesium chloride better suitable.
the individual user within the small range strews the salt in powder form on the frozen-over range.
In the large range of application, particularly in the traffic, it is shifted easily with water and laid on then by means of one at the vehicle fastened centrifuge broad planar. By the damp condition it will not so strongly stand from the wind and remains limited to the roadway.
In order to achieve the full effect on the road, however certain basic conditions must be present. The roadway temperature may vary only within a certain range. If it is too deep, no thawing out effect is to be obtained also with salt. In addition the road must exhibit a certain vehicle frequency that the thawed out ice can also equal up-dry and does not freeze again.
dangers for the environment
the use of thawing salt has some critical disadvantages for the environment. The salt arrives with the meltwater into the soil. There it attacks the root work of plants, which grow at the roadside. Besides thawing salt arrives by various drainage systems into waters and can damage there with certain concentrations Flora and fauna sensitively.
Also with domestic animals, which go through thawed out ice or snow, the salt on the footballs remains, where it can lead to inflammations.
As reaction to it some manufacturers developed a environmentalcompatible thawing salt. In addition by more purposeful use the strewn quantity is reduced, which works both ecologically and economically.
Nevertheless there is a violent for and against the use. Proponents hold out to damaging the environment that the saved accident costs, which consist among other things of direct healing costs of the accident victims and the economic damage by loss of working hours, which exceed costs of the environmental repairs. In addition they refer the dust to the damage, which by the use of strew-split, for example, develop.
In many places and cities therefore for example a general salt strewing prohibition on Gehsteigen, which is waived only in extreme weather, applies.
Web on the left of
- recommendations of the Federal Office for Environment Protection regarding the de-icing salt employment in winter services of the municipalities