What is Colloids: Definition and 18 Discussions

A colloid is a mixture in which one substance of microscopically dispersed insoluble particles are suspended throughout another substance. However, some definitions specify that the particles must be dispersed in a liquid, and others extend the definition to include substances like aerosols and gels. The term colloidal suspension refers unambiguously to the overall mixture (although a narrower sense of the word suspension is distinguished from colloids by larger particle size). A colloid has a dispersed phase (the suspended particles) and a continuous phase (the medium of suspension). The dispersed phase particles have a diameter of approximately 1 nanometre to 1 micrometre.Some colloids are translucent because of the Tyndall effect, which is the scattering of light by particles in the colloid. Other colloids may be opaque or have a slight color.

Colloidal suspensions are the subject of interface and colloid science. This field of study was introduced in 1845 by Italian chemist Francesco Selmi and further investigated since 1861 by Scottish scientist Thomas Graham.

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  1. Dario56

    DLVO Theory of Colloid Stability

    DLVO theory gives the curve of potential energy vs distance of two colloid particles. Potential energy curve is derived for colloids being only electrostatically stabilized and not sterically. Looking at the image below which shows potential energy curve, we can see two local minima and one...
  2. T

    What is the change in entropy for a colloid settling out of solution?

    If it occurs spontaneously then it must increase entropy but the possible micro states reduce so what else is occurring to increase entropy
  3. Asuratyr

    I Can red blood cells be considered colloids? (soft matter physics)

    Hi, I was studying soft matter physics when a question arose between a friend and me. Namely if red blood cells can be considered to be a colloid. Colloids as it was presented to us had 3 criteria: high diffusion so the particles wouldn't form a sediment, a small reynolds number and a surface...
  4. B

    Methods for quantifying colloids?

    What are the methods for quantifying the amount of colloidal particles in sol mixtures?
  5. B

    Is it possible to physically separate colloids from sol'n?

    I understand that colloids (at least those less than 0.7 um in diameter) are not filterable using conventional filters. But are there other physical separation methods that can separate them from solution, apart from using membranes? Centrifugation perhaps? I just want some confirmation. Thank you!
  6. Asmaa Mohammad

    Precipitation of colloidal solutions

    Hello, I read about the colloidal solutions in my chemistry book, and came across this sentence: "Emulsoids (a type of colloidal solutions) are difficult to be precipitated, e.g. by concentrated solution of NaCl (removes H2O film by its osmotic power then it neutralize the charges)." I don't...
  7. M

    Number of closely packed colloidal particles in an aggregate

    Hello everyone This is sort of a geometry problem. I'm sure it has an easy answer but it just won't come to me. Here's my problem A close packed colloidal aggregate of smaller spherical colloidal particles can be thought of as small spheres within a sphere. I have the relationship...
  8. B

    How can we distinguish between colloidal gels and true solutions?

    Hello in class we recently were asked to find a test that distinguishes between a colloidal gel and a true solution. The gel we made in lab was sterno. I thought coagulation or Tyndall effect but not confident in either. Any help is appreciated greatly.
  9. S

    Medical What exactly is the difference between crystalloids and colloids?

    Hello guys, I'm bit confused here, hope you guys can help me out. 1. Crystalloid- Ok they contain water soluble molecules. So eg is Saline (NaCl). Now book says if I infuse crystalloids then only 1/3 of of my infusion would remain in the intravascular compartment. Now my question is why...
  10. T

    Are Nanoparticles Considered Colloidal Systems?

    Hello everybody :smile: I'm not sure if this topic exists but I'm really confused about this thing :shy: I have to write some work about electrostatic stabilisation in nanomaterials and I read a lot but couldn't find anything directly related to nanoparticles. I found only electrostatic...
  11. K

    Average diameters of colloids

    A dispersion of spherical polymer particles contains Np = 4•1013 particles/dm3. The total surface of the particles in 1 dm3 is Asp = 820 m2. a) What kind of average diameter can we calculate. Calculate this average diameter. b) If we know that the dispersion contains 60 vol% water, we...
  12. W

    How does particle size affect drag force in colloids?

    How does one evaluate the drag force on a particle moving through a colloid? And how does this depend on the size of the particle compared to the constituents making up the collloid? For particles much larger than the constituents I can imagine one can just do the same as for a normal fluid...
  13. N

    Trying to understand colloids microscopically and macroscopically

    I've been reading a little about this rather new subject (to me), and I'm quite confused. I understand that a colliod is broadly dfined as a substance consisting of a dispersive phase, ie very finely ground gold dust, in a continuous phase, ie water. I'm informed that colliods are...
  14. T

    Voltammetry of alkylated colloids

    Can anyone point me towards some background reading on how to go about using voltammetry to determine energy levels in semiconductor nanoparticles that are held in colloidal suspension by an alkyl (probably undecyl) monolayer - will this hydrophobic envelope pose problems in terms of getting...
  15. E

    Are Colloids Solid or Liquid and What Modulus is Used to Measure Them?

    are they solid/ liquid? bulk modulus or shear modulus to be used?
  16. E

    Elasticity in colloids (gels, jellies)

    I have a question on finding elasticity of colloids. I am using Ultrasonics testing on testing the different elasticity of gelatine with different concentrations of additives, ie, salt, sugar. From the ultrasonics data, I calculated the attenuation coefficient and the velocity (speed of...
  17. E

    Elasticity in colloids (gels, jellies)

    I have a question on finding elasticity of colloids. I am using Ultrasonics testing on testing the different elasticity of gelatine with different concentrations of additives, ie, salt, sugar. From the ultrasonics data, I calculated the attenuation coefficient and the velocity (speed of...
  18. E

    Elasticity in colloids (gels, jellies)

    I have a question on finding elasticity of colloids. I am using Ultrasonics testing on testing the different elasticity of gelatine with different concentrations of additives, ie, salt, sugar. From the ultrasonics data, I calculated the attenuation coefficient and the velocity (speed of...
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