It's often necessary to determine the solubility of a chemical before you can begin working with it. Chemicals, especially those used in labs, are often concentrated and distilled, in order to be easier to use, transport, and store. But these highly concentrated chemicals will have to be properly reconstituted if they are to be used reliably. The solubility of a chemical is its ability to dissolve when presented with a certain solvent. When it comes to chemicals, it's often important to know how soluble the product is and which solvents are most appropriate for its applications.
What Is Chemical Solubility?
Chemical solubility is a very specific measurement: the maximum amount of the chemical that can be dissolved in a given solvent. Once the solvent has been introduced to as much of the chemical as it possibly can be without beginning to "reject" the chemical, the resulting solution is known as "saturated." A fully saturated solution gives you the solubility of the chemical, but note that this is affected by the solvent as well. It is possible to introduce more of a chemical beyond a certain saturation point, but the resulting mixture will be chemically unstable and will "want" to reject the excess solute.
How Do You Find Solubility?
Most chemicals will have solubility information available already through their vendor. But chemicals that do not have this information available may need to be tested. Generally this is done by introducing a gram (or other measured amount) of the chemical to solvent one part at a time. Another part is added until the solute has been completely dissolved. The amount of parts that needed to be added for complete dissolution is the number of parts that the solute requires to create a saturated solution. Once you know how many parts of solvent and how many parts of solute you need, you can then look at the general solubility descriptions (outlined below). Solubility should almost always be tested at room temperature, as temperature greatly impacts the results.
What Do Solubility Descriptions Mean?
When it comes to laboratory chemicals, very general descriptions are often used to class them into different levels of solubility. Often the laboratory may provide this information to you, both including the number of parts of solvent per solute and the general description of the chemical's solubility. The more soluble the solution is, the easier it will usually be to work with. Here are the terms that you should know.
- Insoluble. If the chemical requires more than 10,000 parts of solvent for a single part of solute.
- Very slightly soluble. If the chemical requires 1,000 to 10,000 parts of solvent for a single part of solute.
- Slightly soluble. If the chemical requires 100 to 1,000 parts of solvent for a single part of solute.
- Sparingly soluble. If the chemical requires 30 to 100 parts of solvent for a single part of solute.
- Soluble. If the chemical requires 10 to 30 parts of solvent for a single part of solute.
- Freely soluble. If the chemical requires 1 to 10 parts of solvent for a single part of solute.
- Very soluble. If the chemical requires less than 1 part of solvent for a single part of solute.
Solubility is very important for those working with chemicals and solutions of all types. Though solubility information should be readily available for most chemicals and compounds, it can sometimes be necessary to either test or verify the chemical's saturation point independently. Luckily, determining solubility is one of the easier techniques to master.
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