Learning to separate different compounds in mixtures is a valuable laboratory skill to learn, particularly learning to separate compounds that are both water-soluble. Both table salt and table sugar are water-soluble compounds, so a run-of-the-mill water filtration will not separate them. Sugar does, however, differ from salt in one way--it is an organic compound. This fact can be exploited to separate sugar from salt.
Evaporate out any water, if necessary, by placing the solution near a heat source. The simplest way to do this is to expose the solution to natural sunlight. This will crystallise the mixture. It is best to separate these two compounds when they are solid crystals.
Put on goggles and gloves.
Pour the salt and sugar crystal mixture into a filter and put that filter over your container. Funnel-shaped filter paper may be best, since this can easily be placed in the neck of a beaker or other container.
Pour your organic solvent carefully into the salt and sugar mixture. This compound will dissolve the sugar, since both the sugar and the solvent are organic---or carbon-containing---compounds. The salt is an ionic compound; therefore its bonds resist the non-polar organic solvent and only yield to only the most polar of solvents, mainly water.
Empty the filter onto a petri dish. The remaining crystals in that were left in the filter should be salt.
Observe the container that you poured the organic solvent into to see if you can save your sugar. Organic solvents like acetone tend to evaporate at low temperatures, and may leave the sugar behind when it does, depending on the solvent's concentration.
You might have to change the type or concentration of organic solvent you use to get a pure separation. You can confirm that you are left with salt in various ways, such as testing the melting point of the crystals
Do not use latex gloves while working with acetone. Perform this procedure in a well-ventilated area.
Tips and warnings
- You might have to change the type or concentration of organic solvent you use to get a pure separation.
- You can confirm that you are left with salt in various ways, such as testing the melting point of the crystals
- Do not use latex gloves while working with acetone.
- Perform this procedure in a well-ventilated area.