In simple terms, ‘miscible’ means ‘mixable’. If two liquids are miscible, it means that they will blend with each other to form an equally distributed, homogeneous solution.
The opposite of miscible is ‘immiscible’, which means that the two liquids will not mix together.
An everyday example of two miscible liquids may be hot water and cold water. These easily mix to form warm water. Another example may be water and juice.
In contrast, an everyday example of immiscible liquids would be oil and vinegar, commonly found in vinaigrette salad dressings. Vinaigrettes eventually separate if left alone, no matter how hard they may be shaken to mix.
Is ‘miscible’ the same thing as ‘dissolve’? No. The word ‘miscible’ is typically used to describe liquids coming together with other liquids; ‘dissolve’ is a term typically used when liquids come together with solids. (See: Solvent: What is Is, What You Need to Know) Technically, solids and even gases can be miscible, but the word is not often used in this context.
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In this article:
- How to Tell if Something is Miscible
- Can Miscible Liquids be Separated?
- Examples of Miscible/Immiscible Liquids
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How to Tell if Something is Miscible
Whether or not a liquid is miscible with another liquid is somewhat determined by whether or not they are of the same nature, or character.
Organic vs Aqueous: Liquids that contain carbon (C) are ‘organic’ by definition and often derived from oil. Aqueous liquids are liquids that are water-based and do not contain carbon. As a general rule, water-based liquids are miscible with other water-based liquids; and organic, or oil-based, liquids are miscible with other organic liquids.
A lot of oil-based products don’t blend with a lot of water-based products. However, there are some cases where organic products do blend with water; whether or not this can happen has to do with the length of the carbon chain. The longer the carbon chain, the less likely it is to go into water. Look at the molecular formula of a chemical for the total ‘C’ value to determine the number of carbons in the molecule. This can give some indication of what the length of the carbon chain might be, and whether or not it will be miscible with water.
The chemical name, also, can often indicate how many carbons may be in the carbon chain. Specific words that make up a chemical name are a direct clue to the number of carbons in the product (or a part of the product).
- Methyl – 1 Carbon
- Ethyl – 2 Carbons
- Propyl – 3 Carbons
- Butyl – 4 Carbons
- Pentyl – 5 Carbons
- Hexyl – 6 Carbons
- Heptyl – 7 Carbons
- Octyl – 8 Carbons
- Nonyl – 9 Carbons
- Decyl – 10 Carbons
Two organic liquids that are miscible with water are Methanol (CH3OH) and Isopropyl Alcohol (C3H8O). These are both simple alcohols that have relatively short carbon chains. Also, they both contain what is called a ‘functional group’ of ‘OH’ (oxygen & hydrogen). This is the same functional group that also makes up water (H2O). Since they are part water already, this helps make it easier for them to go into water.
(The fact that these alcohols blend with water is what makes it possible for products such as Isopropyl Alcohol 70% to exist!)
Density: The density of liquids doesn’t necessarily determine whether or not they will mix, but may affect a solution’s ability to come together quickly (i.e. two water-based liquids that otherwise should come together very quickly may not.)
Can Miscible Liquids be Separated?
If the liquids are both water-based, it will be difficult to separate them after mixing. (It is not easy to get water out of water!)
If the liquids are both oil-based, they may be able to be separated through distillation. All organic liquids have boiling points, and they are not all the same. By raising the temperature of a solution, you may be able to drive one (or more) of the liquids out of the solution without affecting the other. They can then be collected independently of each other.
What about immiscible liquids? Immiscible liquids may be able to be separated by decanting, where one or the other can typically be pulled off the top using a decanter.
Examples of Miscible/Immiscible Liquids
Miscible:
- Vinegar and water
- Milk and water
- Ethanol and water
- Isopropyl Alcohol and water
- Methanol and water
- Honey and water
- Gasoline and oil
Immiscible:
- Mercury and water
- Water and oil
- Vinegar and oil
- Kerosene and water
- Gasoline and water
