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Questions tagged [colloids]

A colloid is a substance in which microscopically dispersed insoluble particles are suspended throughout another substance.

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Why do old black and white photos fade?

I understand why photos based on organic dyes would fade (discussed previously). But photos based on metallic silver fade as well such as like the one shown below. As a metal (a fairly stable one at ...
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How to tell 'orthokinetic' apart from 'perikinetic' based on their prefixes?

During a test in colloid and surface chemistry, students were asked to distinguish between two terms: orthokinetic and perikinetic coagulation. The rate of aggregation is in general determined by ...
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How do xanthan gum and other hydrocolloids work?

Does anyone know what causes things like xanthan gum to make water into a slimy substance on the molecular level?
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Why are critical micelle concentrations so large?

Dissolving a non-polar molecule in water incurs a free energy cost of about $10 kJ/(mol \cdot nm^2)$ (source: http://bionumbers.hms.harvard.edu/bionumber.aspx?&id=101826) The entropy gained from ...
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Brownian motion of colloids at high density

Colloidal particles in dilute suspensions tend to perform a universal type of Brownian motion at finite temperature, according to the Stokes Einstein relation $D\approx\frac{k_BT}{6\pi \eta r}$ in the ...
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Preparation of ferric hydroxide sol

I have read that before the preparation of ferric hydroxide sol, the beaker must be cleaned by the steaming out process, while it is not necessary for starch sol. Why is that?
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Dependence of Osmotic Effects on Particle Size

van't Hof's equation for osmotic pressure is derived with the assumption, among others, that the particle size of the solute is comparable to the particles size of the solvent. It holds well so long ...
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Hypothetically, can sufficiently powerful centrifugation separate normally miscible chemicals of differing densities?

Centrifugation is used to separate phases in suspensions by density. I read that this is not possible with colloids and solutions, but the distinction between the three seems to be optical properties ...
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reduce size of zinc dust

I am working with zinc dust (particles of 10um). I want to make a stable dispersion of this dust with arabic gum. The problem is that the particles are still too big, the solution rapidly settles.... ...
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Manufacturing coloured crystal glass using gold nanoparticles

I came across this video which shows how a crystal chandelier is made. I recommend that anyone reading this post should watch it; it is quite fascinating. Anyway, at about the 2:15 mark, the video ...
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How do I create a transparent liquid for ferrofluid display?

Hello~ I am a media art artists working in Korea. Recently, create a kinetic artwork using ferrofluid. I need to create an artificial pond with a diameter of 3 meters. So I need a lot of suspension ...
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Charges in colloidal dispersion

How does charge come on dispersion medium in colloidal sols ? (It is said that in electro-osmosis flow of dispersion medium takes because it is also electrically charged, but why ? )
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How do lyophilic sols protect lyophobic sols?

How are lyophobic sols prevented from coagulating when lyophilic sols are added to them? I tried to search for the answer but didn't get a plausible explanation anywhere.
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How to keep magnesium hydroxide suspended in water?

How do I keep 8 g of $\ce{Mg(OH)2}$ suspended in 100 mL of water? Milk of magnesium purchased from the store has $\ce{Mg(OH)2}$ well suspended in the bottles. When I make it, the $\ce{Mg(OH)2}$ ...
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Why does it hurt in the mouth when drinking carbonated beverages?

The typical explanation for the origin of the "sting" is that $\ce{CO2}$ turns into carbonic acid (reddit, yahoo), however the "explanations" there are incomplete. The answer I'm looking for would ...
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Diffused Layer ion in Electrix Double Layer

When KI is added to AgNO3 soln, so AgNO3 is in excess, collidal particle is AgI:Ag+ with diffused layer of I-, Why is the diffused layer not of NO3- when the anion in excess is NO3-? If we had KI in ...