Home Podcasts THMG122 – Liquids (Part Deux)

THMG122 – Liquids (Part Deux)


We said we would eventually come around to going a little deeper on some subjects. Well, here is the part 2 for liquids. In this we discuss solubility, miscibility, specific gravity, slurries, emulsions and more.

Thanks for listening and watching!

  1. Intro
    1. We’ve done the basics on all of these point previously, but now it’s time to come back and re-work them a little deeper
    2. In this episode we’re going to investigate the topics:
      1. Solutions, Miscibility and specific gravity
        1. We did a bunch of coverage of this stuff WAY back in Episode 10
      2. Slurry’s
        1. Pretty much every early episode where Bob is drinking
  2. Solutions and Slurries
    1. Let’s define a solution
      1. It’s a physical mixing of compounds into a homogeneous mixture.
        1. OK, Let’s define homogeneous….
          1. That when everything is the same in the mixture
        2. As opposed to?
          1. Heterogeneous. that when it’s not evenly distributed.
          2. Something like Scotch and water would be homogeneous and Sand and water would be heterogeneous.
    2. Back to the matter at hand.
    3. This compound may be a solid, liquid or a gas
      1. The thing we put into a solution is called the solute, and the thing we put it in is the solvent.
      2. So the solvent is what is dissolved into.
      3. This all happens until we reach saturation.
        1. What’s saturation
          1. When no more solute will go into the solvent.
      4. There are things that will influence this. (Hot coffee reference and sugar reference) or Pressure
    4. So what’s a Slurry?
      1. It’s when something is able to suspend in a solution, but not stay up unless it’s agitated.
      2. So usually this is a solute with a high molecular weight, or something that may be ionic.
      3. So something like corn starch in water when you’re making gravy on Sunday. You need to keep stirring to keep it up in the solution.
    5. Why do we care?
      1. It makes a big deal when we are dealing with run off
    6. And just for the record, something can be a solution and a Slurry at the same time.
      1. Think about the hot cocoa you make for the kids. Towards the end of the glass the sweetness stays, but the cocoa falls to the bottom.
  3. Solubility
    1. The term Solubility is usually in reference to water.
      1. Actually 99% of the responders out there listening to us are thinking that.
      2. In reality it’s not like that at all. We’ll come around to that soon.
    2. The loose definition is the maximum amount of a solid, liquid or gas that can dissolve into a liquid.
      1. Now, most of us are thinking about water.
      2. But somethings that are not soluble in water are soluble in alcohol, or ether or something else that works for that particular compound.
    3. We usually see the Solubility of something in weights, or percentages like in the NIOSH. And it’s in reference to a volume. So something is able to dissolve 100g in 100 ml or liquid. Or you can get a gas like 85 cm3 dissolves into 160 ml or water.
    4. And anything like temperature, agitation, pH or pressure can influence this solubility.
    5. OK, Now we’re going to go a little deeper than normal for techs, so strap in.
      1. Solubility as you’ve seen in class is not how it really happens.
        1. See, when we demonstrate solubility we typically show to liquids that are as dissimilar as possible. Something like Vegetable oil and water. this gives a nice clean line for the eye.
        2. Now if we pick something like molasse. This has a solubility of 100%. here’s the skinny on what really happens with solubility.
          1. there are no nice clean lines that are drawn in the liquid.
          2. Actually the line is in some way blurry.
            1. Some of the molasse will dissolve into the water, and some of the water will dissolve into the water.
            2. The number that we typically see in the NIOSH is the number of final solubility after agitation.
          3. So what happens when we change the concentration of the solute? Like for example, if we spill a bucket of solute into water, and the water comes to a “rest”, then we pour a second bucket of solute. Essentially we are doubling the concentration in a static volume.
      2. Let now get into the term “insoluble”
        1. We would define this loosely by saying something that cannot dissolve into the water or solvent.
        2. But this is not really true. There is basically nothing that is 100% insoluble. Even things like Vegetable oil and water has a small amount that can dissolve. It’s tiny, but it’s true.
          1. This is like when you place an object on a granite countertop. You say to yourself that the rock was uneffective. But this is not true. Physics says that the rock will yield a microscopic amount. You may not see it, but it happens (mind = blown)
        3. On the other side of this thought, is something that is 100% soluble also known as miscible?
          1. No. Many people think this is true, but it’s not. there’s a difference.
          2. See, when something is soluble it mixes, but can be separated. but when something is miscible it can be combined in ANY PROPORTION . In Miscibility it cannot be dissociated.
          3. We’ll come back to Miscibility in a bit
    6. Let’s clear up saturation
      1. Let use a simple sample, sugar in water. Or sucrose.
      2. Sucrose has the ability to dissolve into water. Actually LOTS of Sucrose. 200g in 100 ml. When we reach this level, if you keep adding, it will just fall out of the solution and fall to the ground.
    7. Can we just briefly discuss Emulsions?
      1. These are sometimes misinterpreted as a cloudy solution. What they really are is particles in suspension.
      2. Fine oils mixed with water will do this. Take the old standby (water and vegetable oil). Give this a good shake, and you’ll see the water get “milky”
      3. Malathion does this when mixing it. Malathion is mixed with light oils, so when you throw in the water it goes milky and opaque.
  4. Miscibility
    1. Let’s clear this up in a simple way.
      1. In order for something to be miscible it has to have no saturation point.
      2. If there is a point in which you add solute to the solvent and it will come out of solution (no matter what you do to enhance it, more on that in a bit) then it is not miscible.
      3. Miscibility can be done in any proportions and in any manner to never come apart.
      4. I love the example of Scotch and water.
        1. You can put a drop of Scotch into water or
        2. A drop of water into scotch
          1. all the way up to 99% either way.
        3. Now we sit the Scotch out in the sun and let it evaporate.
        4. When you come back, it will be gone.
        5. If this was a saturated solution such as the sat and water that we just spoke about, there would be a residue remaining. Salt will still be clinging to the glass.
        6. Let’s talk about liquids in same solution with varying VP
      5. One last point on this, the term Miscibility is usually used in reference to liquids, less common in both solids and gasses
  5. Specific Gravity
    1. Last point on our tour of liquids and the like
    2. This is a ratio of a solute into water.
    3. We do not use this term when referring to let’s say a solute that dissolves into ethanol. This term is a description of the buoyancy of the material in question.
    4. Now when Mr. Chemistry is asked in class about the specific gravity of something like Acetone. He would quickly look it up in the handy dandy NIOSH. So take a second and answer this question. Based on the NIOSH it says that the SG is 0.78. So what is our damming technique? Over or under?
    5. Here is the part where we blindly read and don’t understand. The solubility of it is listed as miscible. So though it’s “lighter” than water it’s completely integrated with it.
    6. you can get readings in SG for both solids and liquids! Not gases. Makes sense.
    7. Just as a little tip from THMG here’s a couple of rules of thumb that seem to work well in the streets
      1. Most Organics, and hydrocarbons are lighter than water and will float.
      2. Most Halogen acted hydrocarbons are heavier and will sink.
    8. This is one of those properties that will make a huge difference in foam and defensive operations.
The Hazmat Guys

Author: The Hazmat Guys


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