Table Salt: How it is Used in Melting Ice
During winter, snow and ice form in large quantities leading to major transportation problems.
In severe cases they make roads and other passages impassible. Even when snow is just present in moderate quantities it significantly reduce the traction of tires and shoes thus increasing the likelihood of accidents occurring through motor vehicles veering off the road. Not to mention just slipping while walking!
The inconveniences and dangers of having ice and snow on paths, driveways and pavements cannot, therefore, be overemphasized. Whenever they occur various methods are employed to remove ice. Chief among them is the application of rock salt on the ice.
What Kind of Salt is used to Melt Ice?
What is Rock Salt? It is just like ordinary salt in chemical composition but has larger and coarser grains. For over 70 years it has been the main material used in clearing ice from roads and pathways not only in the US but in the rest of the world too.
The United States was, however, the first to use rock salt for ice melting on a large scale.
This was made possible by the large quantities of rock salt that were found in Detroit in the late 19th century. Beginning in 1940 Detroit became the first city to use salt to clear roads and pathways of ice.
Although not frequently used as rock salt, ordinary table salt too can be used to melt ice. In fact, it is far more effective than rock salt at melting ice.
How Table Salt Melts Ice
Like other substances used for melting ice, table salt melts ice by lowering its freezing point. While pure water freezes at 0˚C; the salted water melts at -32˚C. Basically when salt is added to ice it makes it turns to liquid until temperatures drop to below -32˚C.
How does salt achieve this?
Ice usually has a thin layer of liquid water on it. When salt is applied to the ice it dissolves in this water film and separates into sodium and chloride ions.
This solution is called salt melt, or brine.
The ions squeeze themselves between the more tightly packed molecules in ice thus increasing the separation gap between them. As the distance between the molecules in ice increases it becomes liquid.
Table Salt vs. Rock Salt: A Comparison
- Speed – Compared to rock salt, ordinary salt has finer granules. It, therefore, has a much larger surface area than rock salt. This large surface area enables it to melt ice faster because at any given time it will be in contact with more ice particles than rock salt.
- Refreezing – The small particles of table salt have both an advantage and a disadvantage. As discussed in the previous point, their main advantage is the large surface area that makes ice melt faster. However, precisely because of the small particle size, no residue is left after the melting has ended.
This leads to refreezing. The large quantities of rock salt leave a residue after melting thus preventing refreezing of ground cleared of ice.
- Cost – Even though it is more effective, table salt is more expensive than rock salt. While both have basically the same chemical composition, iodine is usually added to table salt during its processing. This processing and addition of other chemicals makes table salt costlier than rock salt.
- Availability – Part of the reason why rock salt is cheap is that it is easily available in large quantities. This makes it ideal for use on a large scale like clearing of roads. For example, it is estimated that in 2013 the quantity of salt used to clear roads in the US was 17m tons. If similar quantities of table salt were to be used it would not only be extremely expensive but also difficult to find such quantities.
The ease of availability and cost of rock salt are the main reasons why it is used more often in large scale to melt ice and snow over table salt, despite it being less effective.
However, there are cases where are table salt is a better alternative.
When and Where Table Salt Can Be Used for Melting Ice
Table salt is best used to melt ice in small quantities where the cost is unlikely to be exorbitant. Places for such usage include short walkways and pavements.
It can also be used when ice needs to be melted quickly for an urgent function.
Best Way to Use Salt for Melting Ice
It sounds simple but many people do not know how to properly melt ice in driveways or walkways.
You don’t just sprinkle and wait!
When the process is messed up the results will always be unsatisfactory. Here is the best way to melt ice.
- Shovel the snow and ice – Shoveling ice is difficult manual work. However, it is important that it is done before any salt is applied. This reduces the quantity of salt that you will eventually apply. This is not only money-saving but is also good for the environment since dissolved salt is harmful to plants, animals and even concrete.
- Applying the salt – When applying the salt make it spread as evenly as possible on the ice. The more salt gets into contact with ice particles the faster it melts.
- Mix the salt with sand – For better traction, apply a mixture of salt and sand to the ice. Even though sand is not soluble, it increases traction of the ground thus making it usable even when all the ice hasn’t melted away.
As shown above, both table and rock salt can be used to melt ice. Each of them has its own strengths and weaknesses. However, regardless of the type of salt you decide to use, you need to carry out the melting process correctly.
Read more about the many uses and benefits of Salt.