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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 is there preferential adsorption of a common ion during preparation of colloids by peptization?

There was a similar question asked here on Chem SE, but the answer was not very satisfactory to me, so I am asking a fresh question. Peptization is the process of creating a colloid from a precipitate ...
Samardeep singh's user avatar
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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 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?
user1669's user avatar
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Do lyophilic sols have an electrical double layer?

"There are two factors which are responsible for the stability of lyophilic sols. These factors are the charge and solvation of the colloidal particles". Quoted from NCERT book of OC But we ...
RIPAN BARUAH's user avatar
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How do lyophilic colloids reduce surface tension?

It's given in my textbook that the surface tension of lyophilic/hydrophilic solutions is lower than water. But my intuition says, since in lyophilic solutions the interaction between a lyophilic ...
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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 ...
Linear Christmas's user avatar
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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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Temperature and zeta potential

What is the temperature effect on zeta potential? My problem was assigned by my teacher for the final exam preparation: "When the temperature is increased, and given in this temperature range, ...
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Why do silver halide crystals in suspension, develop a surface charge

This is a question related to analog photography. Photographic films have a suspension of silver halide crystals in them, and these crystals have adsorptive properties which are used in this ...
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Why are colloidal sol particles of acidic dyes negatively charged and basic dyes positively charged, when it should be the other way round?

From NCERT Class 12 Chemistry; Sri Aurobindo Marg, New Delhi, India; January 2019; p. 136: Colloidal solutions of basic dyes like methylene blue are positively charged whereas colloidal solutions of ...
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How practically to determine dispersion's Hamaker constant using CCC?

I know that Hamaker constants can be determined from CCC data. $$ccc=\frac{9.85 \cdot 10^4 \epsilon^3 k_B^5 T^5 \gamma^4}{N_A e^6 A^2 Z^6}$$ Where, $\epsilon$ is solvent dielectric constant, $N_A$ is ...
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hydrodynamic thickness of polymer vs. concentration of electrolyte?

I've measured the hydrodynamic thickness of a NaPSS layer on polystyrene latex and plotted it against the concentration of the supporting electrolyte, NaCl. My graph shows a general decrease in ...
cjperkie's user avatar
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Estimating maximum size of magnetite particles in this Nile Red ferrofluid video?

In the Nile Red video Making ferrofluid from scratch a suspension of small magnetite ($\ce{Fe^{2+}Fe_2^{3+}O_4^{2−}}$) particles is produced from a combination of ferrous chloride and ferric chloride. ...
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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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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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Will a liquid-liquid emulsion and the separated emulsion have same volume?

Let's assume that there is no dispersed gas (bubbles). Not sure about dissolved gas; maybe you can tell me if that matters. Ordinary liquids (aqueous solution and biological oil). Surfactants are ...
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Brownian motion of asymmetric particles

The classic Stokes-Einstein relation ($D=k_BT/(6\pi\eta r)$) it is assumed that the particle undergoing Brownian motion is spherical, and experiences ordinary Stokes flow between (or during) ...
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When is it realistic to model diffusion without advection?

Brownian motion abounds in nature, but so does drift current. In theoretical models of solutions and colloidal suspensions it is sometimes assumed that advection is negligible. I'm wondering if this ...
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What is the influence of citrate on PEG-modified polyacrylamide hydrogels?

I've been having a puzzle explaining the experimental results with the citrate anions and PEG modified polyacrylamide: According to the experimental data there is a hydrogel swelling whenever citrate ...
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Boilling colloidal silver?

I have some colloidal silver that i bought from a shop. It is 18ppm, however, I need a higher PPM and I can't seem to buy it anywhere where I live. If I boil this colloidal silver, would it make the ...
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How does total depth affect the colloid gradient?

When a colloid reaches diffusion–sedimentation equilibrium, it creates a gradient where the solute concentrates toward the surface or the bottom of the vessel based on its density relative to the ...
Nosajimiki's user avatar
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Gelifying hydrogen peroxide

What substances could be used to gelify 60% hydrogen peroxide? I imagine anything organic like agar would be broken down by the radicals. I tried looking up what dentists use and the only thing 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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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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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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Why is micelle formation endothermic?

Most websites mention that it is endothermic and some mention that it is endothermic at low temp. and exothermic at high temp. Nor do I know the correct answer neither I can guess the reason for any ...
dishant ranparia's user avatar
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What allows for colloidal solutions of polymers to act like solutions despite the large size of polymers?

I have been introduced to a paragraph in my textbook that I am trying to understand. Macromolecular colloids: Macromolecules in suitable solvents form solutions in which the size of the ...
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Particle tracking in colloids and uniformity in fractional part function

I don't know if its right place to ask this question since chemistry and programming both are involved. I was working on particle tracking of series of pictures (.tiff) of colloids. And I was Using ...
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What is the logic behind the terminology lyophilic and lyophobic colloids?

Its given in my text book that- Colloidal dispersions of starch,rubber,proteins etc are lyophilic colloids whereas colloidal dispersions of metals,sulphides etc are lyophobic in nature. But even ...
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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 ...
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