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How can you improve solubility of colloidally dispersed substances?

How can you improve solubility of colloidally dispersed substances?


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If you solve collidally dispersed substances then the particles can form large colloids. This may block narrow passages and diffusion into dense structures may become completely impossible.

What can you do to improve the solubility of such substances?


In my case, three-four rounds of sonication greatly helps in having smaller and more homogeneous hydrophobic particles dispersed in water.


Improving the Water Solubility of Poorly Soluble Drugs

Ideally, drug development would involve the selection of active pharmaceutical ingredients (APIs) that possess ideal drug delivery characteristics, followed by their development using simple dosage forms. However, the reality is that increasingly formulators must work with APIs that have challenging physicochemical properties, including poor water solubility.

The increase in proportion of poorly soluble candidates is attributed to both improvements in synthesis technology, which has enabled the design of very complicated compounds, and also a change in focus in the discovery strategy of new APIs, from a so-called phenotypic approach to a target-based approach. The phenotypic approach involves trial-and-error methodology in which compounds are tested against cells, tissues, or the whole body. This approach takes into account various physicochemical and biological factors that may affect the efficacy of candidates, including solubility, protein binding, and metabolism. In the target-based approach, candidate compounds are screened against specific targets, based on hypotheses concerning action mechanisms. Lead compounds are typically dissolved in dimethyl sulfoxide for high-throughput screening (HTS), which means that even very poorly soluble drugs can be tested. Although the HTS approach provides a clear lead with respect to molecular design, compounds with poor aqueous solubility can progress to development after screening.

Poor water solubility has important ramifications for the drug discovery process, as poorly soluble lead compounds cannot be adequately formulated for subsequent preclinical studies in animals. Thus, it may not be possible to follow up potentially promising leads, which instead have to be dropped from the discovery process, never realizing their true potential. Although it may be possible to overcome the solubility problem by chemical modification of the drug, in many cases this is not feasible.

Poor water solubility also has important ramifications for drug bioavailability. In order to cross an epithelial interface, the drug must usually be dissolved in the biological fluids at that interface. For example, for the oral route, the first step in the oral absorption process is dissolution of the drug in the gastrointestinal (GI) lumen contents. A drug that is poorly soluble in the aqueous GI fluids will demonstrate poor and erratic dissolution, with concomitant low absorption and thus poor bioavailability—even if the drug possesses good intestinal permeability characteristics. Furthermore, the rate of intestinal absorption is driven by the concentration gradient between the intestinal lumen and the blood. A low concentration gradient is a poor driver for absorption, with a concomitant retarded flux across the intestinal epithelium.

As described in detail in Chapter 7, a significant hurdle associated with the oral route is the extreme variability in GI conditions, which can cause large intra- and interindividual variability in pharmacokinetic profiles. Poor water solubility exacerbates this variability, as there is a lack of dose proportionality for these compounds, as well as significant variability depending on the presence of food and fluids in the GI tract. The activity of bile salts on drug solubilization is a further important variable. These formulation and bioavailability concerns are equally relevant for poorly soluble drugs delivered via alternative epithelial routes, such as the pulmonary, topical, nasal, vaginal, and ocular routes.

The Biopharmaceutics Classification System (BCS) classifies drugs into four categories, based on their aqueous solubility and ability to permeate the GI membrane (Figure 3.1). (However, it should be noted that the BCS is relevant to permeation across all biological membranes, not just the GI tract.) Based on pioneering work by Gordon Amidon at the University of Michigan (Amidon et al. 1995), the system has been adopted by the U.S. Food and Drug Administration (FDA) to allow pharmaceutical companies a waiver of clinical bioequivalence studies (a biowaiver), when seeking regulation of postapproval changes and generics. Increasingly, the BCS is being used as a tool in product development, to flag up potential solubility and permeability difficulties that may be associated with lead compounds.

A drug is considered highly soluble if its highest dose strength is soluble in less than 250 mL of water, as tested over a pH range of 1–7.5. A drug is considered high permeable if the oral absorption compares favorably (i.e., higher than 90%) to an intravenous injection of the drug. Absorption in vivo can be carried out by monitoring the appearance of the drug in the plasma after oral administration. Intestinal permeability may also be assessed by other methods, including in vivo intestinal perfusions studies in humans, in vivo or in situ intestinal perfusion studies in animals, in vitro permeation experiments with excised human or animal intestinal tissue, and in vitro permeation experiments across epithelial cell monolayers, such as the Caco-2 cell line.

Using the BCS, four distinct classes of drug can be defined as the following:

• Class I drugs possess characteristics that ensure good bioavailability: they dissolve rapidly in the GI fluids and then rapidly permeate the epithelial barrier.

• Drugs that fall into Class II possess good permeability characteristics, but they have poor solubility, which limits their bioavailability. Approximately 35%–40% of the top 200 drugs listed in the United States and other countries as immediate-release oral formulations are practically insoluble (see also Chapter 20, Figure 20.6). The bioavailability of a Class II drug can be markedly improved by improving its solubility: various methods to improve drug solubility are the focus of this chapter. The fact that about 40% of the top marketed drugs are practically insoluble, yet are nevertheless used commercially, is a testimony to the success of current solubilization methods.

• Class III drugs, although highly soluble, possess poor permeability. Permeability across epithelial barriers and strategies to improve epithelial permeability are described in Chapter 4.

• Class IV drugs have both poor solubility and permeability. In the case of Class IV drugs, improving the solubility may help somewhat toward improving bioavailability, although poor permeability will still be an issue.

Poor solubility and permeability problems may be addressed at the chemical level, via lead optimization: this approach is described in Chapter 20 (Section 20.8). This chapter describes approaches used to increase the solubility of a poorly soluble API. A wide range of approaches can be used, as summarized in Table 3.1.

Which approach to use is partly determined by the nature of the drug. Poorly soluble drugs, i.e., Class II and Class IV of the BCS classification situation, can be further subclassified into two types of molecules (Bergström et al. 2007):

1. “Grease ball”: highly lipophilic compounds, with a high log P (>4) and a low melting point (<200°C). These compounds cannot form bonds with water molecules thus, their solubility is limited by the solvation process.

2. “Brick dust”: compounds usually with low energy, highly stable crystal forms, with a high melting point (>200°C), and with poor water and lipid solubility (log P < 2). The water solubility of such compounds is restricted due to strong intermolecular bonds within the crystal structure.


Preparation of Colloidal Systems

We can prepare a colloidal system by producing particles of colloidal dimensions and distributing these particles throughout a dispersion medium. Particles of colloidal size are formed by two methods:

  1. Dispersion methods: that is, by breaking down larger particles. For example, paint pigments are produced by dispersing large particles by grinding in special mills.
  2. Condensation methods: that is, growth from smaller units, such as molecules or ions. For example, clouds form when water molecules condense and form very small droplets.

A few solid substances, when brought into contact with water, disperse spontaneously and form colloidal systems. Gelatin, glue, starch, and dehydrated milk powder behave in this manner. The particles are already of colloidal size the water simply disperses them. Powdered milk particles of colloidal size are produced by dehydrating milk spray. Some atomizers produce colloidal dispersions of a liquid in air.

We can prepare an emulsion by shaking together or blending two immiscible liquids. This breaks one liquid into droplets of colloidal size, which then disperse throughout the other liquid. Oil spills in the ocean may be difficult to clean up, partly because wave action can cause the oil and water to form an emulsion. In many emulsions, however, the dispersed phase tends to coalesce, form large drops, and separate. Therefore, emulsions are usually stabilized by an emulsifying agent , a substance that inhibits the coalescence of the dispersed liquid. For example, a little soap will stabilize an emulsion of kerosene in water. Milk is an emulsion of butterfat in water, with the protein casein as the emulsifying agent. Mayonnaise is an emulsion of oil in vinegar, with egg yolk components as the emulsifying agents.

Condensation methods form colloidal particles by aggregation of molecules or ions. If the particles grow beyond the colloidal size range, drops or precipitates form, and no colloidal system results. Clouds form when water molecules aggregate and form colloid-sized particles. If these water particles coalesce to form adequately large water drops of liquid water or crystals of solid water, they settle from the sky as rain, sleet, or snow. Many condensation methods involve chemical reactions. We can prepare a red colloidal suspension of iron(III) hydroxide by mixing a concentrated solution of iron(III) chloride with hot water:

A colloidal gold sol results from the reduction of a very dilute solution of gold(III) chloride by a reducing agent such as formaldehyde, tin(II) chloride, or iron(II) sulfate:

Some gold sols prepared in 1857 are still intact (the particles have not coalesced and settled), illustrating the long-term stability of many colloids.


1 Answer 1

Even if you switch to an organic solvent, if the polypyrrole is in water, it will perturb the PEDOT:PSS layer.

Your best bet would be to use a poly-alkyl pyrrole or other conjugated polymer that's soluble in something that doesn't dissolve PEDOT:PSS.

Let's say you switch the solvent to DMF or DMSO and it dissolves the PEDOT:PSS. Then you spin-coat that new mixture onto ITO. Once you drop the aqueous solution of polypyrrole, it will dissolve the PEDOT:PSS.

I think you're looking at this the wrong way. Rather than trying to change the PEDOT:PSS (which will be tricky - PSS is anionic) you should consider changing your polymer. Alternatively, get rid of PEDOT:PSS and use another hole injection layer. (PEDOT:PSS is acidic and will etch the indium out of ITO.)


STUDIES IN THE SEROLOGY OF SYPHILIS

When cholesterinized antigen is dropped into an excess of water, the rapid flocculation of cholesterin crystals is prevented by the fact that, as tiny aggregates form, they adsorb a protective surface of hydrophilic lecithin ( i.e ., antigen) which endows the particles with its own stable surface properties and thus prevents further aggregation. The colloidally dispersed antigen-cholesterin particles have approximately the same isoelectric point (pH 1.9), critical potential (1 to 5 millivolts) and coagulation value (0.75 M NaCl) as pure antigen particles of the same concentration, while the corresponding values for cholesterin are pH 2.1 to 3.4 (probably due to an associated impurity), >100 millivolts, and <0.001 N NaCl, respectively. Presumably, this adsorption of antigen by the cholesterin nucleus is determined by the fact that the former has a lower surface tension against water. At any rate, many surface active substances (serum alcoholic extract of milk, egg or any animal tissue Na-oleate Na-glycocholeate Na-taurocholate) cause a similar stable dispersion of cholesterin and conversely, many otherwise water-insoluble substances of the most diverse chemical structure can be made to form a stable colloidal suspension by adding antigen to their alcoholic solutions before dropping into water. The colloidal suspension formed by antigen alone is very finely dispersed: only a few of the particles exceed the limits of dark field visibility. Cholesterin causes a marked increase in the number of these particles, out of all proportion to its mass thus, one part of cholesterin to five of antigen causes a ten-fold increase in such visible particles, at the expense of the submicroscopic micellae formed by antigen alone. At the same time, the suspension becomes much more turbid. The particles remain discrete until the cholesterin: antigen ratio exceeds 1:1, when slight microscopic aggregation is observed microscopic flocculation is seen only when this ratio exceeds 5:1, when there is not sufficient antigen to act as an efficient protective colloid. Cholesterin therefore causes a coarsened dispersion of antigen by forming a relatively large nucleus upon which antigen is adsorbed. As shown in the text, the larger the antigen particle the greater is its avidity for reagin per unit surface or mass. Thus, the coarse sol formed by dropping water-into-antigen is about twice as efficient as a finely dispersed antigen-into-water sol of the same concentration. The coarsened dispersion caused by cholesterin completely explains the greater sensitivity of the cholesterinized antigen in complement fixation. The same factor obtains in the flocculation reactions. In addition, the coarsened dispersion acts as a preliminary quasi-aggregation, facilitating by just so much the subsequent formation of visible clumps (or sedimenting aggregates) upon the addition of syphilitic serum moreover, there is less surface in a coarse sol, with more reagin per unit surface, and correspondingly more efficient flocculation. The foregoing would be of purely academic interest were it not for the following considerations. From several points of view cholesterin is unsatisfactory as a sensitizer for antigen. Its solubility in alcohol is small. Even the 0.6 per cent concentration used in the Kahn test is difficult to keep in solution. Yet, as our experiments show, its sensitizing action increases indefinitely with its concentration. If it were sufficiently soluble, even 3 per cent could be used to advantage, increasing the sensitivity of 1½ per cent antigen for complement fixation some 200 to 400 per cent, instead of about 50 per cent, as does 0.2 per cent cholesterin. Since, as we have shown, the sensitizing action of cholesterin upon antigen is due solely to the coarse dispersion it causes, and since it is quite inert during the actual combination of the lipoid particles with reagin, it can be replaced by any substance with similar physical properties. The problem in hand was therefore to find a water-insoluble substance, very soluble in alcohol, with so high an interfacial tension against water that, as in the case of cholesterin, microscopic particles would adsorb antigen when the alcoholic solution of the two is dropped into water. Given such a substance, it would be possible to obtain a more sensitive antigen for both complement fixation and flocculation, but particularly for the former. These theoretical expectations have been realized in a group of substances shortly to be reported: they make possible an antigen which is from 2 to 10 times as efficient in the Wassermann test as any now available. Footnotes Submitted: 14 July 1930

Journal

The Journal of Experimental Medicine &ndash Rockefeller University Press


Techniques for preparing solid dispersions

  • Hot melt extrusion method: In the hot melt extrusion process, after the mixture of API, carrier and excipient enters the extruder, the material is first melted under the heating of the extruder barrel and strong shearing force, and then dispersed, distributed and mixed Finally, the material is extruded from the die by the extruder screw extrusion. Technology for preparing solid dispersion-hot melt extrusion method

Spray drying method:After filtering and heating, the air enters the air distributor on the top of the dryer, and the hot air enters the drying chamber evenly in a spiral shape. The material liquid passes through the high-speed centrifugal atomizer on the top of the tower, and (rotating) sprays into very fine misty liquid beads, which can be dried into finished products in a very short time in cocurrent contact with hot air.Technology for preparing solid dispersion-spray drying method

Medicilon’s preparation department can provide the following services:

  • Drug analysis
  • Pre-prescription research
  • Preparation quality research
  • Drug preparation development
  • Quality consistency evaluation of generic drugs
  • Preparation production
  • Clinical trial drug production, outer packaging and labeling

Research and development laboratory equipment of Medicilon

Electrical Properties of Colloidal Particles

Dispersed colloidal particles are often electrically charged. A colloidal particle of iron(III) hydroxide, for example, does not contain enough hydroxide ions to compensate exactly for the positive charges on the iron(III) ions. Thus, each individual colloidal particle bears a positive charge, and the colloidal dispersion consists of charged colloidal particles and some free hydroxide ions, which keep the dispersion electrically neutral. Most metal hydroxide colloids have positive charges, whereas most metals and metal sulfides form negatively charged dispersions. All colloidal particles in any one system have charges of the same sign. This helps keep them dispersed because particles containing like charges repel each other.

We can take advantage of the charge on colloidal particles to remove them from a variety of mixtures. If we place a colloidal dispersion in a container with charged electrodes, positively charged particles, such as iron(III) hydroxide particles, would move to the negative electrode. There, the colloidal particles lose their charge and coagulate as a precipitate.

The carbon and dust particles in smoke are often colloidally dispersed and electrically charged. Frederick Cottrell, an American chemist, developed a process to remove these particles.

Frederick Gardner Cottrell

(a) Frederick Cottrell developed (b) the electrostatic precipitator, a device designed to curb air pollution by removing colloidal particles from air. (credit b: modification of work by “SpLot”/Wikimedia Commons)

Born in Oakland, CA in 1877, Frederick Cottrell devoured textbooks as if they were novels and graduated from high school at the age of 16. He then entered the University of California (UC), Berkeley, completing a Bachelor’s degree in three years. He saved money from his $1200 annual salary as a chemistry teacher at Oakland High School to fund his studies in chemistry in Berlin with Nobel prize winner Jacobus Henricus van’t Hoff, and in Leipzig with Wilhelm Ostwald, another Nobel awardee.

After earning his PhD in physical chemistry, he returned to the United States to teach at UC Berkeley. He also consulted for the DuPont Company, where he developed the electrostatic precipitator, a device designed to curb air pollution by removing colloidal particles from air. Cottrell used the proceeds from his invention to fund a nonprofit research corporation to finance scientific research.

The charged particles are attracted to highly charged electrodes, where they are neutralized and deposited as dust (see the figure below). This is one of the important methods used to clean up the smoke from a variety of industrial processes. The process is also important in the recovery of valuable products from the smoke and flue dust of smelters, furnaces, and kilns. There are also ionic air filters designed for home use to improve indoor air quality.

In a Cottrell precipitator, positively and negatively charged particles are attracted to highly charged electrodes, where they are neutralized and deposited as dust.


Mining chemodiversity from biodiversity of Taxus plants: chemistry and chemical biology

2.9.6 Other uses

A UPLC-MS-MS method was developed to elucidate the impurity profiles of paclitaxel (PTX) and PTX injections from different Chinese pharmaceutical companies ( Zhang et al., 2016 ). The fragmentation patterns for PTX and the related impurities were analyzed and summarized. To remove the interference from auxiliary materials, such as hydrogenated castor oil , PTX was dissolved in ethanol for acid, base, peroxide, and light-induced forced degradation analysis, which could produce all the impurities exist in the PTX injection. Ten impurities were characterized, that is, cephalomannine (1), 7-epi-10-deacetylpaclitaxel (2), 7-epi-paclitaxel (3), baccatin III (4), ethyl ester side chain (5), 7-epi-baccatin III (6), 10-deacetylpaclitaxel (7), PTX isomer (C3–C11 bridge) (8), PTX isomer (9), and N-benzoyl-(2R,3S)-3-phenylisoserine (10). Compounds 1–3 could be introduced during manufacture processing. In the forced degradation studies, the acid-induced degradation products included 3–7, base-induced degradation could produce 2–7 and 10 7 is the main compound produced by hydrogen peroxide treatment, while compounds 3–5 and 7 were produced by high-temperature environment and compounds 2–5 and 9 were from intensity light exposure. Compound 8 was the main impurity from intensity light exposed PTX powder. The results provide an important reference in processing, optimization, quality control, and evaluation of PTX.


Polar Functional Groups

Hydroxyl R-OH

A hydroxyl (alcohol group) is an &ndashOH group covalently bonded to a carbon atom. The oxygen atom is much more electronegative than either the hydrogen or the carbon, which will cause the electrons in the covalent bonds to spend more time around the oxygen than around the C or H. Therefore, the O-H and O-C bonds in the hydroxyl group will be polar covalent bonds. The figure below depict the partial charges &delta + and &delta - associated with hydroxyl group.

The hydroxyl functional group shown here consists of an oxygen atom bound to a carbon atom and a hydrogen atom. These bonds are polar covalent, meaning the electron involved in forming the bonds are not shared equally between the C-O and O-H bonds. Attribution: Created Marc T. Facciotti (Own work)

The hydroxyl functional groups can form hydrogen bonds, shown as a dotted line. The hydrogen bond will form between the &delta - of the oxygen atom and a &delta + of the hydrogen atom. Dipoles shown in blue arrows. Attribution: Marc T. Facciotti (original work)

Hydroxyl groups are very common in biological molecules. Hydroxyl groups appear on carbohydrates (A), on the R-groups of some amino acids (B), and on nucleic acids (C). Can you find any hydroxyl groups in the phospholipid in (D)?

Hydroxyl groups appear on carbohydrates (A glucose), on some amino acids (B Serine), and on nucleotides (C Adenosine triphosphate). D is a phospholipid.

Carboxyl R-COOH

Carboxylic acid is a combination of a carbonyl group and a hydroxyl group attached to the same carbon, resulting in new characteristics. The carboxyl group can ionize, which means it can act as an acid and release the hydrogen atom from the hydroxyl group as a free proton (H + ). This results in a delocalized negative charge on the remaining oxygen atoms. Carboxyl groups can switch back and forth between protonated (R-COOH) and deprotonated (R-COO - ) states depending on the pH of the solution.

The carboxyl group is very versatile. In its protonated state, it can form hydrogen bonds with other polar compounds. In its deprotonated states, it can form ionic bonds with other positively charged compounds. This will have several biological consequences that will be explored more when we discuss enzymes.

Can you identify all the carboxyl groups on the macromolecules shown above?

Amino R-NH3

The amino group consists of a nitrogen atom attached by single bonds to hydrogen atoms. An organic compound that contains an amino group is called an amine. Like oxygen, nitrogen is also more electronegative than both carbon and hydrogen which results in the amino group displaying some polar character.

Amino groups can also act as bases, which means that the nitrogen atom can bond to a third hydrogen atom as shown in the image below. Once this occurs, the nitrogen atom gains a positive charge and can now participate in ionic bonds.

The amine functional group can exist in a deprotonated or protonated state. When protonated the nitrogen atom is bound to three hydrogen atoms and has a positive charge. The deprotonated form of this group is neutral.
Attribution: Created Erin Easlon (Own work)

Phosphate R-PO4 -

A phosphate group is an phosphorus atom covalently bound to 4 oxygen atoms and contains one P=O bond and three P-O &minus bonds. The oxygen atoms are more electronegative than the phosphorous atom resulting in polar covalent bonds. Therefore these oxygen atoms are able to form hydrogen bonds with nearby hydrogen atoms that also have a &delta + (hydrogen atoms bound to another electronegative atom). Phosphate groups also contain a negative charge and can participate in ionic bonds.

Phosphate groups are common in nucleic acids and on phospholipids (the term "phospho" referring to the phosphate group on the lipid). Below are images of a nucleotide monophosphate(A) and a phosphoserine (B).

A nucleotide on the left and phosphoserine on the right. Each has a phosphate group circled in red. Attribution: Created by Marc T. Facciotti (Own work)


Electrical Properties of Colloidal Particles

Dispersed colloidal particles are often electrically charged. A colloidal particle of iron(III) hydroxide, for example, does not contain enough hydroxide ions to compensate exactly for the positive charges on the iron(III) ions. Thus, each individual colloidal particle bears a positive charge, and the colloidal dispersion consists of charged colloidal particles and some free hydroxide ions, which keep the dispersion electrically neutral. Most metal hydroxide colloids have positive charges, whereas most metals and metal sulfides form negatively charged dispersions. All colloidal particles in any one system have charges of the same sign. This helps keep them dispersed because particles containing like charges repel each other.

The charged nature of some colloidal particles may be exploited to remove them from a variety of mixtures. For example, the particles comprising smoke are often colloidally dispersed and electrically charged. Frederick Cottrell, an American chemist, developed a process to remove these particles. The charged particles are attracted to highly charged electrodes, where they are neutralized and deposited as dust (Figure 11.36). This is one of the important

methods used to clean up the smoke from a variety of industrial processes. The process is also important in the recovery of valuable products from the smoke and flue dust of smelters, furnaces, and kilns. There are also similar electrostatic air filters designed for home use to improve indoor air quality.

Portrait of a Chemist

Frederick Gardner Cottrell

Figure 11.35 (a) Frederick Cottrell developed (b) the electrostatic precipitator, a device designed to curb air pollution by removing colloidal particles from air. (credit b: modification of work by “SpLot”/Wikimedia Commons)

Born in Oakland, CA, in 1877, Frederick Cottrell devoured textbooks as if they were novels and graduated from high school at the age of 16. He then entered the University of California (UC), Berkeley, completing a Bachelor’s degree in three years. He saved money from his $1200 annual salary as a chemistry teacher at Oakland High School to fund his studies in chemistry in Berlin with Nobel prize winner Jacobus Henricus van’t Hoff, and in Leipzig with Wilhelm Ostwald, another Nobel awardee. After earning his PhD in physical chemistry, he returned to the United States to teach at UC Berkeley. He also consulted for the DuPont Company, where he developed the electrostatic precipitator, a device designed to curb air pollution by removing colloidal particles from air. Cottrell used the proceeds from his invention to fund a nonprofit research corporation to finance scientific research.

Figure 11.36 In a Cottrell precipitator, positively and negatively charged particles are attracted to highly charged electrodes, where they are neutralized and deposited as dust.

Gelatin desserts, such as Jell-O, are a type of colloid (Figure 11.37). Gelatin sets on cooling because the hot aqueous mixture of gelatin coagulates as it cools, yielding an extremely viscous body known as a gel. A gel is a colloidal dispersion of a liquid phase throughout a solid phase. It appears that the fibers of the dispersing medium form a complex three-dimensional network, the interstices being filled with the liquid medium or a dilute solution of the dispersing medium.

Figure 11.37 Gelatin desserts are colloids in which an aqueous solution of sweeteners and flavors is dispersed throughout a medium of solid proteins. (credit photo: modification of work by Steven Depolo)

Pectin, a carbohydrate from fruit juices, is a gel-forming substance important in jelly making. Silica gel, a colloidal dispersion of hydrated silicon dioxide, is formed when dilute hydrochloric acid is added to a dilute solution of sodium silicate. Canned Heat is a flammable gel made by mixing alcohol and a saturated aqueous solution of calcium acetate.


Watch the video: Disperse System. Introduction. Classification. Colloidal Dispersion (May 2022).


Comments:

  1. Wahkan

    It is no more than conditionality

  2. Suetto

    What a rare piece of luck! What happiness!

  3. Taudal

    This phrase, is matchless)))

  4. Seumas

    No, well, this clearly should not have been posted on the Internet.



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