In this episode, we discuss solubility, miscibility, specific gravity, slurries, emulsions, and more!
Complete Show Notes
4:10 Solutions
- A physical mixing of compounds into a homogeneous mixture
- Homogeneous mixture: everything is equally distributed (i.e. scotch and water)
- Heterogeneous mixture: everything isn’t equally distributed (i.e. sand and water)
- Compounds mixed can be solids, liquids, or gasses
- Things we put into a solution are called solutes, and the mixture we put the solution into is the solvent – in other words, the solvent is what’s dissolved into
- This process happens until we reach saturation, which is the point where no more solute will go into the solvent
9:05 Slurries
- When something can suspend in a solution but can’t stay up unless it’s agitated
- This is usually a solute with a high molecular weight or something that may be ionic (i.e. corn starch in water)
- Slurries are a big deal when we’re handling runoff
- Some things can be solutions and slurries at the same time (i.e. hot cocoa)
12:25 Solubility
- Loose definition is the maximum amount of a solid, liquid, or gas that can dissolve into a liquid
- Some things that aren’t soluble in water are soluble in alcohol, ether, or whatever else works for that particular compound
- We usually see the solubility of something in weights or percentages in reference to a volume (i.e. something is able to dissolve 100 grams in 100 milliliters of liquid)
- Temperature, agitation, pH, pressure, and a number of other factors can influence solubility
- When we demonstrate solubility, we typically show liquids that are as dissimilar as possible (i.e. oil and water)
- If you’re dealing with a substance with 100% solubility, some of that substance dissolves into water, and some of the water also dissolves into the water
- The number we typically see in the NIOSH is the number of final solubility after agitation
- If we change the concentration of the solute, we change the concentration in a static volume
23:20 Insolubility
- Loose definition is something that can’t dissolve into a water or solvent
- There’s basically nothing that’s 100% insoluble – even oil and water have small bits that can dissolve
- Many people think something that’s 100% soluble is also miscible, but that’s not the case
- Soluble substances mix, but can still be separated
- Miscible substances can be combined in any proportion but cannot be disassociated
25:50 Saturation
- Example:
- We’ll use sucrose (a simple sugar) in water as an example
- Sucrose has the ability to dissolve into water – even as much as 200 grams in 100 milliliters
- When we reach these levels, it will fall out of the solution if you keep adding more sucrose
27:35 Emulsions
- Sometimes misinterpreted as cloudy solutions, but they’re actually particles in suspension
- For example, if you shake a solution of water and vegetable oil, the water will get “milky”
29:40 Miscibility
- Miscible substances don’t have a saturation point
- If there’s a point where you add solute to the solvent and it comes out of a solution (no matter what you do to enhance it), it’s not miscible
- Example: scotch and water
- You can put a drop of scotch into water or a drop of water into scotch – all the way up to 99%
- Put the scotch or water out in the sun and let it evaporate
- When you come back, it will be gone
- If this were a saturated solution (like sucrose and water), there would be a residue remaining on the glass
- Miscibility is usually used in reference to liquids and is less common in both solids and gasses
33:50 Specific Gravity
- This is a ratio of a solute into water – description of the buoyancy of the material in question
- You can get readings in specific gravity for solids and liquids, but not for gasses
- Most organics and hydrocarbons are lighter than water and will float
- Most halogen activated hydrocarbons are heavier and will sink
- Knowing these properties can make a huge difference in foam and defensive operations
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