Home Podcasts THMG122 – Liquids, Part II

THMG122 – Liquids, Part II


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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