Viscosity, colloidal solutions

Akers W, Haidekker MA (2004) A molecular rotor as viscosity sensor in aqueous colloid solutions. J Biomech Eng 126(3) 340-345... 

In support of the association theory, colloid chemists cited non-reproduceable cryoscopic molecular weight determinations (which were eventually shown to be caused by errors in technique) and claimed that the ordinary laws of chemistry were not applicable to matter in the colloid state. The latter claim was based, not completely without merit, on the ascerta-tion that the colloid particles are large aggregates of molecules, and thus not accessible to chemical reactants. After all many natural colloids were shown to form double electrical layers and adsorb ions, thus they were "autoregulative" by action of their "surface field" (29). Furthermore, colloidal solutions were known to have abnormally high solution viscosities and abnormally low osmotic pressures. 

II Figure 1). Adsorption continually occurs around the bubbles to replace protein in areas of the interface where coagulation or stretching of the film is occurring. The actual bubble size in the foam depends upon the rate of protein adsorption as well as upon the ease of film rupture. The protein films on adjacent bubbles come in contact and trap the liquid, preventing it from flowing freely. This restriction is governed by the viscosity of the colloidal solution. The polypeptides of denatured proteins situate to positions where their hydrophobic side chains are directed outward toward each other. Because liquid... 

The Einstein theory shows that volume fraction is the theoretically favored concentration unit in the expansion for viscosity, even though it is not a practical unit for unknown solutes. As was the case in the Flory-Huggins theory in Chapter 3, Section 3.4b, it is convenient to convert volume fractions into mass/volume concentration units for the colloidal solute. According to Equation (3.78), 0 = c(V2/M2), where c has units mass/volume and V2 and M2 are the partial molar volume and molecular weight, respectively, of the solute. In viscosity work, volumes are often expressed in deciliters —a testimonial to the convenience of the 100-ml volumetric flask In this case, V2 must be expressed in these units also. The reader is advised to be particularly attentive to the units of concentration in an actual problem since the units of intrinsic viscosity are concentration when the reduced viscosity is written as an expansion of powers of concentration c. (The intrinsic viscosity is dimensionless when the reduced viscosity is written as an expansion of powers of volume fraction 0.) With the substitution of Equation (3.78), Equation (42) becomes... 

Usanovich Academy of Sciences XJ.S.S.R. Department of Technical Sciences, Colloquium on Viscosity of Liquids and Colloidal Solutions 1944 2 86 according to Ghem. Abstr. 40 3318 [2]. 

With regard to their viscosity, nitrocellulose solutions demonstrate the typical properties of lyophilic colloids. The action of pressure, temperature and concentration causes anomalies to appear indicating that these solutions deviate from the... 

Hydroxy propyl methyl cellulose (HPMC).35 HPMC is a partly O-methylated and 0-(2-hydroxypropylated) cellulose available in several grades that vary in viscosity and extent of substitution. It is used widely in pharmaceutical formulations, especially in oral products, as a tablet binder, in film coating, and as controlled release matrix. Soluble in cold water, it forms a viscous colloidal solution. For a 2% aqueous solution (20°C), viscosity can range from 2.4 to 120,000 mPa-s. High-viscosity grades can be used to retard the release of water-soluble drugs from a matrix. 

Sodium alginate35 This material is insoluble in aqueous solutions in which pH is less than 3. It dissolves slowly in water, forming a viscous colloidal solution. Various grades yield various viscosities (1% w/v aqueous solution has a viscosity of 20 to 400 mPa-s at 20°C). Viscosity may vary depending on concentration, pH, and temperature. 

Viscosities of dilute colloidal solutions and dispersions Functions of viscosity... 

The viscosity starts to increase above the CMC and it is well established that the viscosity of a colloidal solution can give information on size and shape of the particles. From studies of the viscosity as a function of micellar concentration, the intrinsic viscosity may be obtained by extrapolation. The intrinsic viscosity depends on a shape factor, and the micelle specific volume and viscosity studies are therefore used to determine micelle shape and hydration. In many cases, these factors appear to be quite constant over a wide concentration range above the CMC. In other cases, such as hexadecyltrimethylammonium bromide (Fig. 2.9), dramatic increases in viscosity are observed at higher concentrations35). Studies of surfactants with low... 

Note from Table 6.8 that the reduced viscosity gives the relative increase in the viscosity of the solution over the solvent, per unit of concentration. Since r/ is the limiting value of the reduced viscosity, it is a measure of the first increment of viscosity due to the dispersed particles and is therefore characteristic of the particles. Equation (6.33) predicts that the intrinsic viscosity should equal 2.5 for spherical particles. If the dispersed phase volume fraction is used to reflect the dry-weight concentration of particles that may become solvated when dispersed, then intrinsic viscosity measurements can be used to determine the extent of solvation as follows. Suppose the mass of colloidal solute in a solution is converted to the volume of unsolvated material using the dry density. If the particles are assumed to be uniformly solvated throughout the dispersion then the solvated particle volume exceeds that of the unsolvated particle volume by the factor 1 + (m], b/m2)(p2/Pi) where my, is the mass of bound solvent, m2 is the mass of the solute particle, p2 is the density of the particle and pi is the density of the solvent. Since 4>[Pg.185]

ALCOGUM 296-W is a high viscosity aqueous solution of sodium polyacrylate. It is an anionic colloid furnished as a whitish colored homogeneous solution at 15% solids, ready for use. 

HAMACO Starches are useful in many applications requiring a water soluble thickener, a protective colloid, bodying agent or binder having the properties of rapid dispersability, specific viscosity and solution stability. The following is a list of recommended applications ... 

The viscosities of solutions of non-electrolytes and of electrolytes ( 13.VIII E) have been extensively investigated those of colloidal solutions will be excluded from consideration here. In the case of non-electrolytes, special attention has been given to solutions of cane sugar, which has been proposed as a standardising liquid. The values below are in centipoises (0 01 poise) ... 

Confer, Viscos, Acad. Sci. U.S.S.R. Conference on Viscosity of Liquids and Colloidal Solutions, Academy of Sciences U.R.S.S., Moscow (in Russian). 

These films can be prepared by a variety of routes, only a few of which are mentioned here. The original references should be consulted for more practical details. Titanium dioxide is used as an illustrative example below. First, colloidal solutions are prepared, e.g., from titanium isopropoxide. The resultant sol is concentrated under vacuum at room temperature until its viscosity increases. Then it is spin-coated on to suitable supports (e.g., conducting glass) and fired in an oven. The firing temperature critically controls the morphology of the resultant film as discussed elsewhere [300-303]. Films up to several micrometers thick can be prepared by this simple version of the sol-gel technology [304]. Aerosol or spray pyrolysis is a somewhat related approach [305, 306]. 

In patients at risk for focal cerebral ischemia, hemodilu-tion has been proposed as a prophylactic and resuscita-tive therapy to ameliorate brain injury. The rationale for hemodilution therapy is based on two facts 1) blood viscosity decreases when blood is diluted with many crystalloid and colloid solutions and 2) an inverse... 

Attwood, D. Currie, L.R.J. Elworthy, P.H. Studies of solubilised micellar solutions 3. The viscosity of solutions formed with nonionic surfactants. J. Colloid Interf. Sci. 1974, 46, 261-265. 

Given a certain support diameter, the immediate formation of a gel film could be promoted by (i) increasing the boehmite concentration, (ii) ageing the colloidal solution and, (iii) in some cases the dipping time [3]. In later studies [12,14] additions such as PVA were added which enhance the viscosity of the colloidal solution and promote the formation of a lyogel film. 

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