In a summer as hot as ever, chilling drinks becomes a biological imperative, but sometimes we get distracted and forget to refrigerate a few bottles. What should we do in these cases? The trick of wrapping wet paper around the bottles is always valid, but now we'll reveal an even more formidable trick: use salt. Using salt to freeze drinks faster is a simple yet effective method that exploits the principles of physical chemistry. To understand the phenomenon, it's necessary to delve deeper into the concepts of freezing point and freezing point depression. Let's see what it's all about.
How Salt Makes Drinks Cool Faster
According to the Encyclopedia Britannica, freezing point depression is largely responsible. When salt (sodium chloride) is added to ice, the salt dissolves in the liquid water on the surface of the ice, forming a saline solution. This lowers the freezing point of water, meaning the saline solution remains liquid at temperatures below 32°F/0°C, the normal freezing point of pure water. The freezing point is the temperature at which a liquid becomes solid.
Salt is beneficial because when added to ice, it dissolves into the "melted water" that forms on the surface of the ice. This process requires energy, which is removed from the surrounding environment in the form of heat, causing the temperature to drop further. Adding salt causes the ice to melt more (which is why it is thrown on paved roads in harsh winters) because the salt solution has a lower freezing point than pure water. This leads to a situation where salt water and ice coexist at a temperature lower than the normal freezing point of water. While water freezes at 32°F/0°C, the salt solution freezes at -7.6°F/-22°C. This creates an extremely cold environment around the drink, which accelerates the cooling process. The drink surrounded by this icy salt solution cools much more quickly than when immersed in just ice.
How does this translate into practical terms? Imagine having a bottle of wine in an ice cooler: the wine will cool as heat is transferred from the bottle to the ice. However, if you add salt to the ice, lowering the freezing point of the solution, you will create a much colder environment around the bottle. This increased temperature difference between the drink and the outside environment accelerates the heat transfer, consequently cooling the wine more quickly.
The same applies to maintaining the temperature: if we take the bottle from the refrigerator at 41°F/5°C and place it in a cooler filled with ice with the outside temperature at 86°F/30°C, it takes about an hour to bring it to room temperature, or 86°F/30°C, turning the wine into a broth. If we add salt to that ice, however, it takes a full 3 hours to reach that temperature.
What is The "Recipe" for Salt in Ice to Chill Drinks?
We need to understand some factors about freezing point:
- The more water you have, the more salt you will need because things go in proportion.
- The more salt, the faster the cooling.
- Coarse salt is more effective due to the specific weight of the grains.
In general, a 20% solution is recommended, i.e. 200 grams of salt per 1 liter of water to bring the freezing point down to 14°F/-10°C.
Adding salt to ice in a container is a simple and effective way to speed up the chilling of beverages. This method is particularly recommended for uniform containers, such as cylindrical cans, but it's also highly effective for bottles of various types. The only advice we can give you about wine is that, if the bottle is particularly valuable and you want to preserve it after you're finished, rinse it once it's up to temperature, as salt can ruin the label.
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