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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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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 ...
Gokul's user avatar
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11 votes
2 answers
785 views

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 ...
Crystal Lettuce's user avatar
10 votes
0 answers
879 views

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 ...
JM97's user avatar
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8 votes
2 answers
6k views

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 ...
Aakash Kumar's user avatar
8 votes
1 answer
626 views

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 ...
blackcornail's user avatar
7 votes
3 answers
17k views

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 ...
stochastic13's user avatar
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7 votes
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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 ...
Dissenter's user avatar
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7 votes
1 answer
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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 ...
Starboy's user avatar
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6 votes
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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
5 votes
2 answers
799 views

Name of particles in a suspension

What is the proper name given to the particles in a suspension? Suspensae perhaps? When these particles are brought out of suspension, and precipitate down to the bottom of the mixture, what is that ...
hotmeatballsoup's user avatar
5 votes
2 answers
78 views

Why are nanoliposome encapsulated antibiotics still so unavailable despite being so effective?

I wasnt sure how the phrase the headline question really nor if this is the right place to ask it, but i'm primarily interested in the chemical synthesis aspect and the experience of chemists ...
Furious Gamer's user avatar
5 votes
1 answer
156 views

Bond-order parameter $g_6(r)$

I would like to know the explicit steps to compute the bond correlation function $$g_6(r) = \langle\Psi_6^*(0) \cdot \Psi_6(r)\rangle$$ for colloids in my experiment (2D). I have the position of all ...
user239504's user avatar
5 votes
1 answer
3k views

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 ...
Siddharth Venu's user avatar
5 votes
2 answers
338 views

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.
Elene F.'s user avatar
5 votes
1 answer
559 views

Charge acquired by sols after their preparation

This table from my textbook (p. 20), shows nature of charge on particles of listed sols, in their original or natural form. What reasons can be attributed to oxides (sols) being positively charged? ...
Harshil's user avatar
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4 votes
2 answers
389 views

Weirdness From Boiling Gold Colloid Dry

I was doing an experiment in my chemistry class and found something odd. We prepared a colloid of gold with the following procedure. 1: Measure out 20ml of Hydrogen Tetrachloroaurate (iii) in grad ...
NerdyDude's user avatar
4 votes
1 answer
2k 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 ...
Arpita Karkare's user avatar
4 votes
1 answer
523 views

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 ...
Renier's user avatar
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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 ...
MolbOrg's user avatar
  • 141
4 votes
1 answer
191 views

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 ...
Black Jack 21's user avatar
4 votes
1 answer
229 views

How to prevent sedimentation of an EDTA suspension?

I tried to create a suspension of EDTA powder in glycerin with 1:1 ratio. I keep facing problem of EDTA sedimentation. I've tried other ratios also but this was the only one which formed least amount ...
Sohail SA's user avatar
4 votes
0 answers
150 views

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 ...
A.K.'s user avatar
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4 votes
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168 views

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
3 votes
1 answer
286 views

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 ...
Paze's user avatar
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3 votes
2 answers
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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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3 votes
1 answer
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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 ...
Ignacio's user avatar
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3 votes
2 answers
64k views

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....
Jomar Dy's user avatar
3 votes
0 answers
128 views

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
3 votes
0 answers
181 views

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 ...
R. Anusha's user avatar
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0 answers
578 views

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
3 votes
0 answers
151 views

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 ...
Mark Eichenlaub's user avatar
2 votes
2 answers
411 views

What kind of solution is formed when alkali metals are dissolved at high concentration in liquid ammonia?

When an alkali metal is dissolved in liquid ammonia, it results in the formation of a deep blue coloured solution. $$\ce{M + (x + y) NH3 -> M+(NH3)_x + e^-(NH3)_y}$$ The ammoniated electrons absorb ...
Shashaank's user avatar
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2 votes
2 answers
870 views

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 ...
user47125's user avatar
2 votes
1 answer
50 views

Watercolor pigment conundrum - can a change in ionic profile induce flocculation?

A client of mine has installed an ion exchange water purifier to de-harden her tap water. After that, however, she noticed that it has negatively affected her watercolor painting. From what she ...
Alex's user avatar
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2 votes
1 answer
3k 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.
nimishxotwod's user avatar
2 votes
2 answers
784 views

How does adding HCl convert AgCl into a sol?

According to the text I follow, in peptization the ions of the added electrolyte (peptizing agent) get adsorbed by the particles of the precipitate and turn the precipitate into a sol. An example of ...
Arnab Chowdhury's user avatar
2 votes
1 answer
561 views

Why does a low concentration of soap in water behave as a strong electrolytes?

According to my text, "a colloid in which the dispersed phase consists of micelles is called an association colloid." An example would be soap in water. They use the term 'associated colloid' and '...
Arnab Chowdhury's user avatar
2 votes
1 answer
243 views

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,...
Peter's user avatar
  • 21
2 votes
1 answer
1k views

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 ...
닥드정's user avatar
2 votes
1 answer
77 views

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 ...
user40014's user avatar
  • 517
2 votes
0 answers
55 views

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, ...
Shira's user avatar
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2 votes
0 answers
51 views

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 ...
febot's user avatar
  • 21
2 votes
0 answers
376 views

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 ...
Tatai's user avatar
  • 317
2 votes
0 answers
28 views

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 ...
Alex Alex's user avatar
  • 121
2 votes
0 answers
75 views

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
2 votes
0 answers
218 views

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. ...
uhoh's user avatar
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2 votes
0 answers
104 views

How to charge titanium dioxide particles for a DIY e-paper capsule? [closed]

I'm trying to make a single e-paper capsule (1 cm × 1 cm) at home. At first, I tried to charge the $\ce{TiO2}$ particles by putting them in $\ce{H2O}$ with $\ce{NaOH}$ and then putting that whole ...
JingleBells's user avatar
2 votes
0 answers
53 views

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 ...
BatWannaBe's user avatar
2 votes
0 answers
104 views

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 ...
TLDR's user avatar
  • 143
2 votes
0 answers
551 views

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?
Sharat's user avatar
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