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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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Formation of silica from TEOS

Usually tetraethyl orthosilicate/tetraethoxy silane (TEOS) is mixed with both ethanol and water to produce silica in a sol-gel process. I am curious what happens if one adds TEOS to water at a high pH,...
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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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1answer
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What decides the nature of emulsifying agents?

I read The emulsifying agent forms an interfacial film between suspended particles and the medium. The principal emulsifying agents for O/W emulsions are proteins, gums, natural and ...
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What is the chemistry behind black colour of platinum black? [duplicate]

Platinum is a silvery white metal and is highly unreactive then why it's powdered form "platinum black" is platinum metal but is black in colour. why would a metal such as platinum become black as a ...
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Hardy Schulze law

I have trouble understanding this particular law. It states that: Greater the valency of the flocculating ion, greater will be its coagulation power. Why does this happen? What is the intuition ...
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Why do properties of colloidal solution depend only on dispersion medium's physical state? [closed]

According to a past year JEE question, properties of colloidal solution depends only on dispersion medium's physical state and not on nature of dispersed phase or dispersion medium, or temperature of ...
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72 views

Colour of colloids

Why colours of colloidal solutions are different when viewed along different directions? For example Milk appears blue when viewed by reflected light and red when viewed by transmitted light Is it ...
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Why does the colour of gold sol change with particle size? [duplicate]

Regarding the colour of gold sol, my book says Finest gold sol is red in colour; as the size of particles increases, it appears purple, then blue and finally golden. This is the image I found on ...
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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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What is “gold number”?

I was reading about gold number and a book defined gold number as following: It is the minimum mass in milligrams of a stabilizing agent which is added to the 10 mL of red gold sol to protect it ...
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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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How can I get a hand sanitizer solution to form a gel?

I am trying to formulate a gel hand sanitizer for a thesis project. The sanitizer that I have right now is watery and will not gel. My teacher told me to change our formulation because it is not good....
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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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Is it possible to prevent agglomeration and sedimentation of microparticles just by increasing the viscosity of the medium?

I am considering a suspension of a fine powder in a high-viscosity liquid. The suspension shall be stable over long time scales, i.e. the particles only move a few mm per year, and I have the ...
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Does MgCl2 sol coagulate gold sol faster than Fe(OH)3 sol?

Here is a question from the former AIEEE 2005 The disperse phase in colloidal iron (III) hydroxide and colloidal gold is positively and negatively charged respectively. Which of the following ...
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The entropy change during micellization

I was reviewing the thermodynamics of micelle formation from the Wikipedia page and this book. I understood most of the arguments but micellization is supposed to be an entropy driven process with a ...
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1answer
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What is the modern hardware/supermarket term for 'laundry bluing'?

I want to make this amazing paper Crystal Tree with my kids. One of the ingredients is laundry bluing. It is described thus: The magic crystals that are left behind are a combination of the Mrs. ...
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1answer
355 views

Why don't particles of a colloid settle?

Why don't particles of a colloid settle but those of a suspension do? - Is it because they are really small and so remain in constant motion which overcomes the force of gravity and prevents them ...
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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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Movement of solid particles in colloids

A liquid is made up of tiny vibrating particles of matter, such as atoms, held together by intermolecular forces. Where a solid is the same, but the atoms have much less freedom of movement. Even if ...
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107 views

Permanent cloudy colloid with water

I need to make a cloudy white liquid where the particles won't eventually settle out. It will be exhibiting the Tyndall effect for a very long time. I'd use milk, but I don't want it to become rancid....
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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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1answer
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Can cationic species form micelles?

Most of the books dive into formation of micelles by soaps. They go on talking about alkyl sulphate and carboxylates, but never do they mention anything about cations. My textbook says that at ...
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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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Is it possible for the remaining solute of a saturated solution to form a single even phase from top to bottom (similar to that of a colloid)?

If a solute that dissolves in a liquid solvent has reached high enough levels to cause saturation within the solution, is it possible for the remaining solute particles to form an evenly distributed ...
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1answer
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Is there a way to find the mixture type with just the molecular formulas and masses of the solute and solvent?

If you had the molecular formula and molar mass of a solvent and a solute and no other specific information about the two, could one deduce the type of mixture (suspension, colloid, solution) they ...
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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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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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2answers
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Conversion between anisotropic temperature factors and geometric ellipsoids

I am using the ANISOU of the PDB standard to represent ellipsoid shaped colloids. I am writing a Monte Carlo simulation to transform the position and orientation of the ellipsoids and want to use a ...
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2k views

How can proteins reduce surface tension?

How can the protein lactalbumin reduce the surface tension of water and work like an emulsifying agent in milk?
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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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Water purification procedure that does not involve a flocculant of any kind?

I have read about "electroflocculation" that uses less flocculant/alum, but is there a method – no matter how expensive or impractical – that uses no flocculant at all?
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Any example of colloidal solution where liquid Helium is solvent?

I would like to see any information, if it exists, about colloidal solutions where Helium is "solvent". Background of that question is, I'm wondering giving surface energy effects, how potentially ...
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899 views

Reaction of Iron(III) with hydroxide ion

The observations: 1) Treatment of 1 mL of 0.05 M $\ce{Fe(NH4)SO4}$ solution with excess 1 M $\ce{NaOH}$ results in the formation of a rust-colored red-brown iron-based solution with many suspended ...
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What is the molecular mechanism behind oncotic pressure?

I can't wrap my head around the idea of oncotic pressure and osmolarity, logically. I imagine a blood vessel. It is filled with proteins, like a ton of proteins and solutes. So this means, according ...
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Separating Lipids from Milk

I am trying to develop a procedure to test the percent mass of lipids in (update: homogenized) milk. It doesn't need to be very accurate, just an interesting application of chemical principles. As I ...
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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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Colloids dispersion classification

I've been teaching chemistry for 25 years, but now I'm confused. Is a colloidal dispersion a heterogeneous or homogeneous mixture? I've seen both answers on the web.
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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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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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1answer
709 views

Light scattering in sulfur colloids

Recently I did a reaction in the lab (the reaction itself is not important) whose product was colloidal sulfur. As I watched the sulfur particles form I noticed something strange: At first the sulfur ...
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Do Faraday's gold colloidal solutions still exist?

The Royal Institution seems to claim that they still possess some of Faraday's original gold colloids: "These liquids are some of the first examples of metallic gold colloids, made by Michael Faraday ...
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1answer
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Interaction between metalic nanoparticles and aggregation

I can't find any publication to deal with aggregation of colloidal metalic nanoparticles. What type of interaction(s) is/are there between aqeous metalic nanoparticles which give(s) rise to ...
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1answer
271 views

Formation of sulfur colloids

What happens when we pass sulfur vapors through cold water? What is the reaction for it? Which type is colloid is this? And why doesn't it form in hot or lukewarm water
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The sponge isn't foaming up, why?

When I add dish soap to a sponge it is able to foam up. But if I leave the sponge alone for an hour, it doesn't foam up, not even if it is wetted. Why? The sponge should still contain dish soap an ...
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1answer
773 views

White of an egg

What happens when you dissolve white of an egg in water? Firstly, what's white of an egg? Is it the white part? Or implies whole of an egg? I couldn't relate much of it with colloids, either.
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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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Scattering of light

How does the path of light become visible due to scattering of light? According to me it only indicates the presence of colloidal particles, but my book gives the example of a cinema hall projector ...