Which law is used for stability of emulsion?
Stokes’ law is an equation used to calculate the terminal velocity of a hard sphere falling through a continuous medium makes use of a dynamic viscosity, but as we’ve seen emulsions are often non-Newtonian and show shear thinning behaviour with increasing shear rates.
What is Stokes’s law and how is that related to instability of emulsion?
Stoke’s Law calculates rate of destabilization of an emulsion by equating gravitational force with the opposing hydrodynamic force. Stoke’s Law can be used to predict emulsion stability. Stoke’s Law calculates rate of destabilization of an emulsion by equating gravitational force with the opposing hydrodynamic force.
What is creaming and Stokes law?
Creaming is the movement of oil droplets under gravity to form a concentrated cream layer at the top of an O/W emulsion. Stokes’ Law tells us that the creaming speed v of an isolated rigid droplet of density ρ and radius a is. 2.7.
How is emulsion stability calculated?
The turbidity measurement is a simple and inexpensive method of determining the stability of an emulsion. It represents an indirect method for evaluation of emulsion stability by correlating the particle size distribution and the turbidity of colloidal systems.
What causes flocculation in emulsion?
Flocculation is when the emulsion droplets aggregate and thereby form larger units. Coalescence is when smaller droplets merge together forming a larger droplet. This occurs when droplets come in contact with each other and the interfacial film is ruptured. Eventually the phase separation will happen.
What is the difference between creaming and sedimentation?
Sedimentation and creaming are two analogous phenomena, but in one case, “particles” in the liquid have a density higher than the liquid, and in the other case, the density is lower. In other words, in one case, particles fall, but in the other case, they float.
What is the pH of emulsion?
For batch emulsions prepared at pH 3.4, oil-in-water (o/w) emulsions are formed that are stable to coalescence but exhibit creaming. Below pH 3.3, however, these emulsions are very unstable to coalescence and rapid phase separation occurs just after homogenization (pH-dependent).
What is difference between flocculation and coagulation?
Coagulation and flocculation are two separate processes, used in succession, to overcome the forces stabilising the suspended particles. While coagulation neutralises the charges on the particles, flocculation enables them to bind together, making them bigger, so that they can be more easily separated from the liquid.
What is flocculation of emulsion?
Flocculation is the process in which the emulsion drops aggregate, without rupture of the stabilising layer at the interface, if the pair interaction free energy becomes appre- ciably negative at a certain separation.
What causes phase inversion in emulsion?
Phase inversion can be induced by shifting the emulsifier affinity from one phase to the other, which is called transitional phase inversion. It can also be triggered by a change in the water-to-oil ratio of the emulsion, which leads to a process known as catastrophic phase inversion.
What is difference between creaming and cracking?
Creaming occur when isolated oil droplets combine and rise to the top of an oil water emulsion or sink to the bottom in w/o emulsions. In both scenarios, the emulsion can be easily re-dispersed by shaking. Coalescence (breaking or cracking) is the total and irreversible division and fusion of the dispersed stage.
What is breaking in emulsion?
The “breaking,” or “resolution,” of an oil in water emulsion is done by neutralizing the charges at the surface of the droplets. This is performed with a cationic emulsion breaker because the dielectric constants of oil and water cause the oil droplets to carry a negative charge in water.
How does pH affect emulsion?
Emulsions were highly unstable at pH 2.5, with their emulsion-stability index declining almost three times more than that of other emulsions during the storage time. Based on the size distribution data, a direct correlation was not observed between droplet size distribution and emulsion stability.
How can you reduce the viscosity of emulsions?
The simplest way to achieve a viscosity reduction is to heat the product because most liquids become less viscous when they heated. The viscosity decrease is usually accompanied by a decrease in the interfacial tension, more readily making a good emulsion form.
Can Stoke’s law predict emulsion stability?
Stoke’s Law can be used to predict emulsion stability. 1. Stoke’s Law Photo courtesy of Patrick Willems on Flickr Prof. Abd Karim Alias Universiti Sains Malaysia
How do you use Stokes’law to calculate viscosity?
Knowing the terminal velocity, the size and density of the sphere, and the density of the liquid, Stokes’ law can be used to calculate the viscosity of the fluid. A series of steel ball bearings of different diameters are normally used in the classic experiment to improve the accuracy of the calculation.
How do you calculate the rate of destabilization of an emulsion?
You can change your ad preferences anytime. Create your free account to read unlimited documents. You are reading a preview. Create your free account to continue reading. Stoke’s Law calculates rate of destabilization of an emulsion by equating gravitational force with the opposing hydrodynamic force.
What is Stoke’s law in chemistry?
Stoke’s Law calculates rate of destabilization of an emulsion by equating gravitational force with the opposing hydrodynamic force. Stoke’s Law can be used to predict emulsion stability.