If you accidentally added salt to the sugar bowl or sugar to the salt shaker, your best bet is to ditch the mixture and start over. However, if you are interested in separating the salt from the sugar as a scientific experiment, there are certain ways to accomplish the task. Although, it should be clear that of the two methods described in this article, one is simple and safe but arduous and is never completed successfully; while the other is a scientific experiment that can be very dangerous without proper precautions, knowledge and supervision. Do not attempt the second method unless you are well versed in security protocols and have proper supervision and instruction.
Part 1 of 2: Attempt mechanical separation
Step 1. Evaluate the different grain sizes of salt and sugar
At first glance, table salt and granulated sugar are very similar, including the size. However, the minuscule differences in the average grain size of the two do offer an option to attempt separation.
- Common table salt has an average grain size of 100 microns, or 0.01 mm. Keep in mind that other types of homemade salt, such as kosher salt or salting, will have widely divergent average grain sizes.
- Common granulated sugar has an average grain size of 500 microns (0.5 mm), or is five times the size of table salt. Again, the other sugars, like powdered sugar or brown sugar, will have very different average grain sizes.
Step 2. Get a sieve that is somewhere between these grain sizes
Laboratory sieves (or strainers) are measured by the gaps between the mesh. You want to find one that is large enough to allow the salt to pass through, but small enough to prevent the sugar from passing through.
Since salt is 100 microns long and sugar 500 microns, a 250 micron (0.25mm) sieve would be a good intermediate alternative
Step 3. Shake
This method is as simple as it sounds. Add small amounts of the salt and sugar mixture at a time to the sieve (with a bowl underneath) and shake, shake and shake to slowly but surely pass enough salt through the mesh openings into the bowl.
- Since this method depends on the difference in average grain sizes, it will never be completely successful. There will be a few smaller grains of sugar that will sneak in and some larger grains of salt that will linger, not to mention those that can stick; at least to the point where you get tired of sifting.
- However, despite its limitations, sifting is a legitimate scientific means of separation. Just don't expect to use the separated sugar in your coffee, unless you want a salty taste!
Part 2 of 2: Dissolve and evaporate the mixture
Step 1. Consider a safer and simpler alternative to a science experiment
If you teach or learn how to separate materials or prepare solutions, think about using salt and sand as the materials to be mixed together instead of salt and sugar. It's a little easier, safer, and just as interesting.
- Separating the salt and sand involves adding warm water to the mix to dissolve the salt, strain the sand by pouring the water mixture through a fine sieve, then carefully heating the water to set the salt aside. This does not involve flammable liquids or potentially dangerous gases.
- Safety issue is likely the main reason why it is difficult to find legitimate scientific curricula or recommendations on how to separate salt and sugar. However, if you insist on doing so, take all precautions. Do not try this at home unless you are well versed in chemistry and have followed all safety measures.
- First of all, always have a working fire extinguisher nearby.
Step 2. Add ethanol to the salt sugar mixture
The higher the amount of salt and sugar, the more ethanol you will have to use. There should be enough alcohol for the sugar to dissolve without becoming too saturated.
If possible, consider using only a small amount of salt and sugar, or separating into parts if you have a large amount. Ethanol is flammable and using too much will increase the risk of a fire
Step 3. Mix the solution with a spoon or a mixing stick to dissolve the sugar
Once the mixture sets, the salt should be at the bottom of the beaker.
Granulated sugar is an organic substance that is soluble in alcohol and other organic solvents (for example, acetone). However, table salt is much more soluble in alcohol than in water, since the lower polarity of the latter provides less attraction to the sodium in the salt and to the chlorine ions
Step 4. Pour the alcohol solution into a new container through a very fine strainer
The strainer should have collected all the salt particles. Let the strainer dry, then pour the salt into another container.
Remember that table salt has an average grain size of 100 microns, so you will need a strainer whose mesh openings are smaller than that measurement. Perhaps you can use a coffee filter inside the strainer instead
Step 5. Wait for the alcohol to evaporate or create a steam bath
To prepare a steam bath, place a small pot one-fourth full of water on a heating element. Make sure you can place a glass bowl directly over the pot so that the bottom of the bowl doesn't come into contact with the water inside the pot.
A steam bath is similar to the water bath used in the kitchen
Step 6. Place the ethanol and sugar mixture in an open bowl on the steam bath
Turn on a fan or hood, and wear a mask so you don't breathe in alcohol fumes.
- Only after placing the alcohol solution in the upper bowl, heat the water over medium heat to a slight boil. The steam bath is designed to slightly heat the solution due to the volatility of the alcohol. Other methods can spark and ignite the alcohol.
- Do not let the alcohol solution come in contact with the heating element or any open fire.
- Stay away from the steam that forms on top of the open container that holds the sugar and alcohol as it distills.
Step 7. Continue the process until all the alcohol has evaporated
The sugar will stay in the open container. Pour it into a different container.