Talk:Salting out isopropyl alcohol

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This article should be renamed to something like "Drying isopropyl alcohol", "Removal of water from isopropyl alcohol", "Removal of water from organic solvents", or even "Drying organic solvents", as this chemical process applies to many organic solvents, including ethanol and other alcohols.

The current title of "Salting out isopropyl alcohol" is uncomfortable. The instructions suggest using "Non-iodized salt", which is just pure sodium chloride or table salt.

More information about drying agents. [1]


Step 1: Research

Many organic solvents are immiscible with aqueous solutions, but able to dissolve significant amounts of water because of their polarity. Fist you must decide on a suitable drying agent for your chosen solvent.

This article uses sodium chloride (non-iodized table salt) because it is easy to obtain, but drying agents most often used in organic laboratories include calcium chloride (CaCl2), sodium sulfate (Na2SO4) calcium sulfate (CaSO4, also known as Drierite) and magnesium sulfate (MgSO4), all in their anhydrous form.

Isopropyl alcohol, like ethanol, forms an azeotrope with water, with a boiling point of 80.37 °C (176.67 °F) and a maximum composition of 87.7 wt% (91 vol%) isopropyl alcohol. [2].

Step 2: Preparation

Fill a glass container with your chosen solvent, then slowly add an appropriate volume of drying agent.

Approximately one quarter of the container's volume of sodium chloride (table salt) should be added to the isopropyl alcohol. Other drying agents may be more or less effective.

Step 3: Mixing

If the container can be sealed, shake the solution thoroughly for at least 5 minutes. Otherwise use a stirring rod, spoon, or magnetic stir bar to stir the solution until no more salt will dissolve.

Step 4: Separation

Leave the solution undisturbed for approximately 30 minutes to allow the mixture to separate from the water into distinct layers, the top of which is concentrated isopropyl alcohol. Preferably use a separating funnel to remove the water solution, otherwise siphon off the top layer using a syringe, and placed in an airtight container for storage. No salt should be siphoned and a thin layer of organic solvent should be left in the container to avoid any salt water being drawn up.

Discard the aqueous layer as it contains only salt and any trace impurities which have a higher affinity for dissolving in water over your chosen organic solvent.

Step 5: Distilling

Using distillation apparatus, you can concentrate the solution even further by heating to its boiling point and condensing its vapours into another container.

Boiling isopropyl alcohol and other organic solvents can be very dangerous as they are often inflammable, so should only be done with proper equipment.