If you accidentally add salt to the sugar bowl or add sugar to the salt bowl, the best option is to discard the mixture and use new sugar or salt. However, if you are interested in separating salt and sugar as a scientific experiment, there are several ways to do it. However, of the two methods listed here, one method is safe but difficult to do and often fails. The other way is chemical experiments which can be very dangerous without proper precautions, knowledge of how to carry out, and supervision. Don't try the second method unless you have good security protocols in place and proper supervision and/or instructions.
Step
Method 1 of 2: Attempting Mechanical Separation
Step 1. Pay attention to the different grain sizes of the salt and sugar
At first glance, table salt and sugar look almost the same, including the size. However, the difference in average grain size between salt and sugar provides an opportunity for separation.
- Table salt usually has an average grain size of 100 microns or 0.1 mm. Note that other types of household salt such as kosher or pickle salt have very different grain sizes.
- Granulated sugar usually has an average grain size of 500 microns (0.5 mm) or five times the size of table salt. Again, other sugars such as powdered sugar or brown sugar have very different average sizes.
Step 2. Use a sieve that is in between the sizes of these two grains
Laboratory sieves (or sieves) come in various sizes based on the mesh spacing. Mesh is the number of holes in the sieve per 1 square inch (6.5 square cm). You'll need to find a sieve that's big enough to let the salt fall, but small enough to keep the sugar from falling.
Since salt is 100 microns and sugar is 500 microns, a 250 micron (0.25 mm) sieve is a good choice
Step 3. Perform sifting
This step is as easy as it sounds. Add a little bit of the salt-sugar mixture to the sieve (with the bowl underneath). Then, shake and move the sieve slowly but steadily to drop the salt through the sieve holes into the bowl.
- Because this method relies on differences in average grain size, it doesn't always work. There will be smaller grains of sugar so they will fall through the hole and there will be larger grains of salt so they don't fall. Plus, the grains may stick together – at least until you get tired of sifting through them.
- Despite these limitations, screening or sifting is a good scientific way to perform the separation. Just don't use separated sugar in your coffee, unless you like it salty!
Method 2 of 2: Dissolving and Evaporating the Mixture
Step 1. Consider an alternative, easier and safer way of scientific experimentation
If you are teaching or learning to separate ingredients and/or make solutions, consider using salt and sand in your mixture instead of salt and sugar. The salt and sand mixture is easier to separate, safer, and just as attractive.
- Separating salt and sand involves adding warm water to the mixture to dissolve the salt, filtering the sand by pouring the water mixture through a fine sieve, then boiling the water to precipitate the salt. This separation does not involve flammable liquids or hazardous gases.
- Safety concerns are the main reason why it's so hard to find good work plans or scientific advice on how to separate salt and sugar. However, if you still want to do it, take precautionary steps. Do not do this at home unless you are an expert in chemistry and have prepared all safety measures.
- First and foremost, always have a fire extinguisher near you.
Step 2. Add ethanol to your salt and sugar mixture
The more salt and sugar you mix, the more ethanol you have to use. You should use enough alcohol so that the sugar dissolves without becoming saturated.
If possible, consider using a little salt and sugar or separating it several times if the amount is large. Ethanol is flammable and using a lot of ethanol can increase the risk of fire
Step 3. Stir the solution with a spoon or stir bar to dissolve the sugar
Once the mixture settles, the salt will be at the bottom of the beaker.
Granulated sugar is an organic substance that is soluble in alcohol and other organic solvents (such as acetone). However, table sugar is more difficult to dissolve in alcohol than in water because the lower polarity of water results in lower attraction for sodium and chlorine ions in salt
Step 4. Pour the alcohol solution through a very fine sieve into a new container
Your sieve or sieve will collect all the salt particles. Allow the sieve or sieve to dry and pour the salt into a separate container.
Keep in mind that table salt has an average grain size of 100 microns so you will need a sieve or sieve with holes smaller than that. You may be able to use a coffee filter placed in the sieve
Step 5. Wait for the alcohol to evaporate or make a steam bath
To make a steam bath, place a small saucepan about a quarter of the water on your heater. Make sure that you can place the glass bowl directly over the pan so that the bottom of the bowl doesn't hit the water in the pan.
Steam boilers are similar to double boilers used in cooking
Step 6. Place the sugar and ethanol mixture in an open bowl over the steam bath
Use a fume hood and wear a mask to prevent inhalation of alcohol vapours.
- Only after placing the alcohol solution in the bowl, heat the water over medium heat. The steam bath is designed to heat the solution slowly due to the volatility of the alcohol. Any other way can cause a spark and burn the alcohol.
- Do not allow the alcohol solution to come into contact with heaters or other open flames.
- Stay away from the vapors that build up over an open container of sugar and alcohol as the mixture is filtered.
Step 7. Continue the process until all the alcohol has evaporated
The sugar will settle in an open container. Pour the sugar into a separate container.
